For an inspection mirror I prefer one larger than the typical dental mirror, and an auto parts store will have one with a swivel and telescoping handle for just a few bucks. I use mine all the time.

As for attaching a strap button, any acoustic guitar tech worth his salt can install one, even if it requires a backing block. This is a common fit, one I have done many many times. If you were nearby, I'd do it just to be Mudcat (good verb, eh!).

I like your fannypack style perch idea, and it'll be lighter than the stand you sometimes see performers (Santana is one) use to quickly go back and forth between instruments. I'm sure I would use the stand if I was in your situation. It has padded clamps to hold the instrument and is adjustable for height and neck angle.

Good luck!

Peace, Mooh.