Old ro units/parts laying around? Need o-ring.

[ScubaSteve]

For future reference, if you are having trouble find parts like o-rings, or anything for that matter, try McMaster-Carr (http://www.mcmaster.com). They carry almost anything you'd ever look for and they ship usually within a day or two if they have what you are looking for in stock (which they usually do). I've had a few devices that used non-standard sizes for o-rings; McMaster had them for less than what the manufacturer was going to sell me a replacement for.