If you have to buy new ones, do they have any "sport" lenses? I.e., they look a bit like goggles and are held on via a strap, not ear-pieces. I think the lenses are plastic.

Another question, since I'm not sure I've pieced it together enough (and I'm braindead from an extended stint with cleaning the stairs off) -- how vital is it that he have glasses while he's destroying them? (I didn't get mine till I was about 7-8, and while I probably should have had them sooner... (I'd forgotten what airplanes looked like! If I ever knew...) I coped. But I just had myopia.)

Good luck.