There are some being marketed especially towards gliders, should be equally useable for you. You'll have to carry some kind of battery, though, which may be a lot of weight. Ah, I see you are already carrying a battery for the radio, well, if it is juicy enough it can supply the transponder, too. When not transmitting, i.e. when not interrogated, power draw is quite limited, at least for the newer generation solid state transponders.
Last edited by Jan Olieslagers; 6th Mar 2016 at 06:47.