retnug once bubbled...
In my limited research on HID lights it seems that most if not all bulbs are manufactured by Welch-Allyn and are very expensive. That seems to be where most of the HID dive light manufacturers claim to get the bulbs that they use in costructing their lights. That is if they even tell you at all. The "developers" kits from Welch-Allyn, if memeory serves, are pretty expensive ($500 per bulb/ballast) and may require you to buy a minimum number. I could be off there a little.
There also appear to be different types of ballast and bulbs. Some are slightly different while other's specs seem to differ greatly. It's hard to tell because the bulbs and ballast seem to have pretty scarce markings on them. How will you know if you buy the correct bulb for the ballast.
In other words you may be stuck with buying the bulb from the manufacturer of your light.
If anyone else has found out anything different I would be really interested to hear it.
Gunter