I've been using the boosters from Hobby King in HK.

http://www.hobbyking.com/hobbyking/s...idProduct=7884

Last time I ordered I bought a couple dozen, looks like I've got about a dozen left. In any sort of quantity they're $5-6 (shipping ain't cheap from HK).

They appear to have the same general specs as the TQ unit (2.7-4.2v input, 5v output @ 1a constant / 1.5a burst), have the advantage that they can plug in between the esc and receiver for esc's that will support this (Novak, etc) OR we use a 3" servo extension with one end cut off and solder to where power lands on esc and plug through for Tekin, etc. The Novak booster has more current capability and runs at 6v out, neither of which is needed and the size is ridiculous.