[winger]

Someone at Newtonville Camera might know of one - 617 965 1240. They always had the ads for the co-op in with the darkroom stuff.

You could also find the Danforth Museum School out in Framingham and ask them. I used to take classes there and they had open time on Saturdays and you didn't have to be taking a class there. If you talk to the right person (no, I don't know who that is), you might be able to get time in there on your own schedule.