In the meantime, consider starting your own worm bin. With the right conditions they'll multiply very fast. If you've got the space and can control the environment look into an outside worm bed (protect from cooking in the sun, freezing in the winter, controlling moisture, protect from predators). People have use old tubs as their worm bed. Lots of options. But at $4 for 50lb, if nothing else you could consider it inexpensive compost.