This tiny video transmitter for FPV RC planes and multirotors seems to work every bit as big as the larger units -- plus it has the bonus of 32 channels and far lighter weight.
Can't really think of any negatives for this unit and it's perfect for 250-sized multirotors and smaller fixed-wing craft like the AXN.
These transmitters are available from a number of online retailers and seem to sell for around US$30 or so.
The unit reviewed here was purchased from HiModel.com