In reply to Madden:
I'd ask him what works for him, whether he has any ideas and I'd see if you can share the routefinding time with your other clients assuming you're in a group. It gets everyone thinking about how to climb which is good for them as well as the guy who needs holds identifying (presumably there are several problems per panel so simply feeling for them is not an option).
Rare earth magnets taped to bits of wool would make for a quick, safe, re-useable way of marking the way to the next hand hold if he likes that idea but it's not so good for the feet.
Presumably he's going to need a spotter to help with awkward landings, landing safely without depth perception is not easy. There's also the day to day stuff like not climbing over people or walking under them that will be a challenge. In that case a bit of teamwork on the route finding is probably still the best approach.
Have you tried the BMC, CWA and the RNIB to see if they can point you toward anything or anyone?
jk