It's going to be a tough nut to crack.
One avenue that you might want to try is the originations that help out people that need prosthetics.
Perhaps not for the main portion of the devices, but maybe ancillary 'add-ons'. Perhaps mods for vehicles or scooters or even wheelchairs.
Now I'll bore you with two stories of 'trying'. It's tough sometimes.
Back in the late '90s I bought a home from a widow, the husband had just passed away after a long term illness.
House needed a bit of TLC and she was headed for a retirement community.
She asked if I could handle the 'stuff' she needed to leave behind because she just didn't have the resources to get it cleared out.
Scored some sweet items in the garage, he had been a machinist, but then there was 'the room'.
Totally equipped, medical room, for lack of better words. From a hospital style bed to a wheel chair to a walker.
It took me three weeks to find an organization to take it, and more importantly - put it to use.
I could have just donated it to any number of organizations for re-sale.
Finally ended up connecting up with an obscure Veterans group that I'd never heard of.
They had a Vet who was in need of all of the equipment, immediately. So that worked out, just took awhile.
But all the other 'main stream' organizations' I contacted weren't able to find a need for the equipment.
Next one was 9/11. I had (4) dish-pak boxes of 3M series 6000 respirators along with filters from an auction.
After watching the recovery efforts in NYC and seeing first responders wearing paper masks, I figured I'd try to get them up there somehow.
I knew the crew at a major airline here, and one of the managers said he could put them on a plane to Newark but we needed to find someone to 'receive' them at that end.
Spent three days making calls and posting on newsgroups, but never was able to find any entity to receive them at Newark.
Ended up donating them a few years later to Habitat...