I've never seen any of the pygmy species for sale, but they are often quite common. Pullosquilla is probably one of the most abundant of all stomatopods. It occurs from French Polynesia to Africa and we have often recorded densities in the sand of 20 or more per square meter. They are really interesting animals. They are spearers, reach a maximum length of about 18 mm, live in u-shaped burrows about 8 inches long and 6 inches deep, are monogamous, and the males participate in the care of the eggs. In fact, they are one of the very few crustaceans with biparental care. In the lab we keep them in "ant farms" that allow us to see into at least part of the burrow. Both the male and female hunt picking plankton from the water column. They do very well on live adult brine shrimp and even though they mature sexually in just a couple of months, I have kept individuals for at least three years.
Another species of spearer, Parvisquilla is even smaller, but it lives in worm tubes in massive coral heads and is very hard to find. I've only seen four in 30 years of smashing up Porieties rubble. We don't even know if they are monogamous, etc.
Taku is the smallest of all smashers and lives in rubble in high energy reef crests. They are fairly easy to collect (I can get five or six a day on the Great Barrier Reef), but nothing has been done on their behavior.
Roy