I know these are expensive, but there are guitar stands that can be used in the standing position. One of our classical guitar professors at school uses it all of the time. Course, you can't move around. The stand takes all the pressure and does all of the holding. I've seen a strap that crosses between the shoulder blades on your back. That strap is available through elderly instruments at www.elderly.com. Rick Fielding makes guitar straps. Send him a PM and he might have some suggestions. You may have to wait for an answer though, owing to his illness.

W.E.