You could try replacing just the light-bulb part and re-using the reflector, as was done by the photographer on this link . . .

http://www.theonlinedarkroom.com/201...-bulb-fix.html


I always read that the original bulbs (Philips 6604) were out of production decades ago, and that the more recent one (Philips 13139, having a different mount to the 6604) is also now out of production but can still occasionally be found. The Osram has very different specs for the reflector so is rather sub-optimal. A couple of years ago I found a machined aluminium adapter to take the 'new' bulb in the 'old' style of enlarger and, although that was expensive at the time, it does work - if you can find the bulbs.