I believe you can purchase them from Carolina Biological Supply Co.- last
number I have is (800) 334-5551 for the N. Carolina division and (800)
547-1733 for the Oregon division. While they are generally a bit pricy,
once you've set up a colony I don't think they're that difficult to breed.
I had a similar situation some years back when I was breeding scorpions,
and ended up ordering a wingless variation of Drosophilia (fruit flies).
They bred like crazy and were a perfect meal for the tiny fellas.