Based on the age, and if the lamps page doesn't yield any results, I would suggest calling up ADJ directly, but instead of going to service, ask to speak to the PARTS department. Chances are they'd have an answer for you, either positive(yes, we have them OR "we don't carry that bulb but this is the replacement for that") or negative(sorry, we don't carry that anymore).
Best of luck to you. As most of us know, many bulbs work in many different fixtures, thank goodness. I'm willing to bet that ADJ will have a suitable substitute bulb for you.