RE: Please help out one arm club member
There is an article in the January 1990 issue of Model Aviation by M. McGee on WOBBLE STICKING. It shows how to modify a four channel radio to be operated with one hand using a "wobble stick." The radio is mounted to a block of styrofoam that is hollowed out to sit over the flyer's thigh. Velcro straps could be used to keep the radio/block assembly secure. The article can be found in the MA digital archives in the members' section of the AMA website.
Looks like it would be a less expensive alternative to having a single stick transmitter built.