Source for OPD valves for aluminium tanks:
in stock at Out Doors Mart, NC. I think the price is a bit stiff: they are $28.95, plus shipping of about $7.00 (approximate until an address is given). They have a small quantity for 40Lbs, a lot more for 30Lbs. They can get more in just a few days.
These Manchester valves are certified to be the right ones: on 02/21/03, I have personaly checked the stamping on shaft as 5.8" (for 30) & 7" (for 40Lbs).
phone: 800 ODM CAMP http://www.outofdoorsmart.com/
[PS: I said price is stiff, but I really don't know: we paid $20, but they were the wrong ones.]