Thanks. We do have one of those companies... a few years ago, I took an old empty CO2 extinguisher to them to pressure-test the bottle (only). That's all I asked for, not to certify it as an extinguisher or guarantee it for use. They did nothing for 2 weeks, then said "the valve was leaking so they couldn't test the bottle" but they'd be glad to sell me a valve for $95 and then test it (and charge more).
Haven't been inclined to do any more business with them. But I might have to grit my teeth and give them a call...