1. I just bought today two replacement bulbs for my enlarger. I bought them in OSRAM shop. So, try with OSRAM or Philips, or General Electric, or simillar (maybe from Japan?)bulb manufacturer... I belive you have (some of) those companies dealers in Hong Kong, and if you can not place 220V bulb in your enlarger, you (probably) should have no problems to order 120V bulbs at those dealers. That is, if your enlarger use bulbs which are not specially made for that enlarger type, bur commonly avaliable at bulb manufacturers..
For correct type of bulb, check enlargers manual...
I found these web sites:
Dead Link Removed
http://www.replacementlightbulbs.com/index.html
2. I don't know your enlarger, but if your enlarger doesn't have trensformer or some electronic circuits in itself, I mean if its only have cable and bulb carrier, then you probably can use 220V bulb in it, if bulb for 220V has same size (if 220V bulb can fit into bulb carrier) as 120V bulb. Problem with that can be that cable is maybe to thin (because it is made for lower, 120V), and maybe you must replace for thicker cabe, for 220V. If you don't know how to do that, or your enlarger have transformer or electronic circuits ask some electrician to make adjustments for you. NOTE! If you follow my advices, you are doing that at your own risk. I am not responsabile if anything goes wrong! If you are not shure what you are doing, or not shure if you want to do it in at all, DO NOT follow my advice!
3. If you can't buy original replacement filter drawer somewhere, I would second what Neal said. Do it youself, or find someone to make drawer for you.
Best luck.