Funny, just saw this post and I am doing just that. I got a gremlin in my system. It burned out a bulb in an old headlamp I have. A few weeks ago I dropped my perfectly good old lamp and broke the glass, bulb was ok. So today I peeled out the old glass , cleaned it up, and very carefully made five small cuts into the top half of the good lamp ( @9-3-10-2 o'clock), bent back the lip and slipped the old lamp glass in and curled the lip back and then put a bead of silicon around the lip (old silicon gasket was still in place and intact around the I side lip of reflector . Works. Theses are supposed to be a sealed beam lamp so these are not meant to be taken apart, but the cost and availability of new ones lends itself to give it a shot. No loss, everything to gain Maybe somebody out there has kept and old burned out one. There is a place that sells a replacement reflectors with glass that uses replacement halogen bulbs. You'll have to search the forum or it. Found it.
http://www.charlies-place.com/