Which is an unsupervised place where people with disabilities can go and get, return, or exchange equipment such as wheelchairs, crutches, etc. Somewhat like a public bookcase, but for equipment.
So this is for permanent personal use? More commonly seen are complimentary lending of mobility aids in malls, museums, and other large facilities for short use inside.
The closest comparison I can think of is akin to a shop=hearing_aid + fee=no if that works for hearing. So shop=medical_supply + medical_supply=mobility + fee=no + self_service=only ? It’s unfortunate “supply” may be more associated with consumables, but equipment is included.
If a government or some public organizations provide free medical equipment or even service, the same shop= or amenity= may still be used. It’s not absolutely necessary to break away from private practice.