Freeze dried cultures available from ATCC - can be prepared, transferred to beads in cryovials and stored at -70degrees. Environmental isolates can also be stored in this way.
Alternatively, try Quanticult... system is available for most of the microbes used in growth promotion testing. Cells are reconstituted in small vials, and give cell counts of 10-100cfu per 0.1ml. A bit more expensive, but really nice and easy.