If he's small enough to still be eating 1/4" crickets, then I would stay away from meal worms or any worms that are too big.
You can get calci worms at some pet stores, which are the same as phoenix worms. I haven't seen phoenix worms for sale in any of the petstores I've been in.
You can order them off the internet from a bunch of places, though.
Feed your bd as many crickets as it will eat in 10 or so minutes. I drop them in about 6 at a time, so I don't have to chase down the ones she won't eat... My girl is about 5.6-6" from nose to tail and eats about 25-30 1/4" crickets, some greens, and a few phoenix worms daily.