Couple of ideas:

1) If you use batteries, the recharger doesn't have to
supply enough power to operate the rig at maximum
demand - only average demand. If a rig draws 4 W on
receive and 20 W on transmit, and you transmit 10% of
the time, a 6-7 watt source should be more than enough.

2) A small solar panel can provide a trickle charge for
NiMH/nicad batteries. Of course it doesn't work at night.

3) Costco and others sell a small crankpowered LED flashlight. No
springs - winding the crank charges the batteries.

4) Or you could follow G5BD's example:

http://jacksonharbor.home.att.net/g5bd.jpg

73 de Jim, N2EY