You can build one from radio shack parts. & run it off a RC pack.
you'll need a RC repair kit
the right size power adapter
& the cord that fits that adapter.
Splice the rc end on the cord from the repair kit. Crimp it. put the adapter on & your done. it's about 14 bucks in parts + the Battery
Real easy to do. & if the Radio Shack employee isn't a dumbass they should be able to point you in the right direction.
Check the archive for instructions on the UA-5 cable.