Don't know if PA law will allow this gambit, but it has worked for me once. Under Louisiana law a doctor may prescribe any "handicapped assistance" device (or creature, I know a lady with s seeing-eye pig) that he determines to be of utility to the handicapped patient.
I built a delta trike conversion with an HT 50 cc engine and just took my chances on the roll cage requirement. I rode it to my Dr's office, he came out and putted around the parking lot on it (he's 67 himself) and loved it. He wrote a prescription for its use, which I kept with it (put it in a ziplock bag, rolled it up tight, and slid it into the handlebar) Unfortunately, it was destroyed last year while parked by a guy who backed over it with a full size pickup, then drove away quickly. He really wrecked it - frame bent beyond repair, engine jug cracked, exhaust broken off, engine mounts broken loose.
I've designed a rear suspension tadpole recumbent to be powered by an R/S 35 and GEBE rig, and have most of the parts fabricated (bed rail angle iron is great stuff) - now I need to get the ladder frame and drop axle welded up, start assembly. Unfortunately, medical costs are eating me alive (dialysis is expensive), so it is slow going just now.
One of my dream trips would be to take that thing, once completed, to eastern Tennessee, and drive the Blue Ridge Parkway. My family originated in that area, and I have a huge number of cousins of various degrees all over that country. Maybe someday.