Gina, the old link I had no longer worked but when I did a new search for "rice hulls" in Phoenix CL, that's the site that loaded for me and still shows up if I refresh.  For some reason, some formatting here by F4F was messing with the link even though it appeared okay.  I edited it to html and seems to work fine when clicking on it now.  The second link is also broken, copy and paste to get to the horse supply place's page for rice hulls with descriptions (it is the web site for the seller, phone number is the same, that's how I found their web site.)  Yes, they are selling rice hulls for horse stalls.  Somebody at f4f mentioned them a few weeks ago saying they had just got some bags (SoCal?) from them to use for media.

Harvey, That should work. There should be no shortage of rice hulls in northern California. The boiling inactivates left over rice grains and weed seeds. The people at riceland have figured out how long the hulls need to be at boiling to accomplish that. That may be in some of the papers I have. I'll double check to see if I can find that number.

Gina, The boiling is apparently required to inactivate rice seeds and weed seeds. There may be some other desirable, physical changes to the hulls caused by parbroiling. 

A friend (partner in one of my farming ventures) grows a couple of hundred acres of rice but the mills are north of us and I don't recall ever seeing what was done with them when I worked up in the Yuba City area (middle of rice country) in the 1980s.  If I can get them delivered that inexpensively or just get some in a nearby feed store, I'll give them a try.

Harvey, Get to researching and you discover where your understanding is off. Here is a good explanation of the process of creating parboiled rice and the parboiled rice hulls that are a by product.
http://en.wikipedia.org/wiki/Parboiled_rice
So, the husks (bran) themselves are apparently not treated after removing the rice in this process. It looks like any rice miller that produces parboiled rice should have the parboiled hulls. This is the best list I have found to date about millers in the US. 
http://www.usarice.com/index.php?option=com_membership&view=suppliers&layout=supplier&Itemid=147
This is a better list of California millers. My guess is the product they call "stabilized rice bran" is parboiled hulls.
http://www.calrice.org/Industry+Info/For+Industry+Members/Commercial+Contacts.htm
If you can find a California source through any of your contacts, that would be WAY cool. There are clearly rice millers in California producing parboiled rice. What they are doing with them is anybody's guess.

I don't think my understanding was "off".  I believe most rice here in California is not parboiled so most rice hulls that are available have not been parboiled.  I believe parboiled rice is usually sold as "pearl" rice.  I used to know more about this when I worked in financing rice farmers but that was a long time ago.  I know where the closest mill is located but am pretty sure they don't want me showing up to get a pickup load.

I called Cathy at Perma Stall (links above) and she said they do deliver to various feed stores in California and I might be able to drop off a load near me but it might need to be 16 pallets worth (6CF/50 pounds each).  The "organic" additive they coat the hulls with is diatomaceous earth but it's a small quantity (helps reduce insects in horse stalls).

The potting mix place in Sacramento gave me a quote for the mix I discussed in the OP and it's too high, $86/cubic yard.  I had asked her if they used rice hulls in their mixes and she said they don't use them much as they blow around in their yard and contaminate their bins of other material.

By the way, a friend in San Diego told me that he buys perlite in 6 cubic foot bags at Apache Perlite for $6.50/bag which is pretty attractive (other than the dust).

I am starting to like the expanded clay pellets (one brand is hydroton) in my mix I am only trying it out this year so far but they are light weight, they are more sparse than perlite since they are bigger but it is still keeping it more open soil imo.  We will see how it does in the summer time but I don't think it will be a problem.

Chivas, how large is hydroton?  I wanted something about 1/4" mostly and, in my quest, had stopped by a hydroponics shop that only had #3 and #4 sizes which were maybe 1/2"-3/4" in size (#3) and maybe 3/4"-1" in size (#4).  That is way bigger than what I wanted but I guess the pot growers use it for hydroponics and I had read also that orchid growers use it for media.

The ones I got were 8-16 mm (.3-.6 inches)  They have larger sizes but like you, I wanted the smaller ones.  Where I work they used to grow roses and they would put 2-4" of the hydroton on the bottom of the pot so the roses wouldn't have wet feet and for diesease pressure etc. 

It's not the greatest to have such variation in the size but eventually maybe I can find more uniform product, when they get into the larger pots like 20 gallon, I doubt that it will be much issue.

I had to order them for the same reason as what you said, the shops around here are not carrying the size that I wanted.

DWD2, the stabilized rice bran is not the hulls.  The hulls are the outer shell which is removed and separated from the rice grain.  The bran is the outer layer of the rice after the hull is removed.  The rice bran contains oils which cause it to go rancid and when it is stabilized the oil is removed which gives it a longer shelf life. 

Chapman, Thanks! My knowledge about cereal grain anatomy is slim.