There is a great machine shop down who's name escapes me. Over by Western Marine(drive north on Clark until it dead ends, on 1 st I think. turn right at the end of Clark and it will be almost immediately on your right, green awnings, before Western.) They machine all our prop shafts and couplings and make new keys for us(3"dia is biggest I've personally taken to them).
I'm not sure if they produce on site, we usually buy shaft out of the us. If they don't, they'll know who in town would.
Lovely shop set up, I'd love to have some of their toys!
Edit: quick turn around too, 2-3 days normal for us though at this time of year you might have a bit of a wait.