I would incorporate the wheel chair as part of the camera support. Others have mentioned the “super clamp” and “magic arm”, and similar items, and that would probably be the best approach. Or, you might have something fabricated especially for that particular wheel chair, making it an integral and permanent part of the wheel chair. I’m thinking about an aluminum arm with a camera mount, hinged to the wheel chair, that could be swung out when needed, with a single leg which extends to ground level for support. Very quick to set up, and no matter where you went, one could say “tripods are not permitted here”. Talk to a local metal fabricator.