As it's been a while since you asked and no answers have been forthcoming, let me offer these suggestions:
History - Nelson used to make the cannisters in Neilsville, WI as directed by their corporate headquarters on Highway 51 in Stoughton, WI. Nelson was bought by Fleetguard (Cummins) a few years ago.
1. Calling Nelson/Fleetguard in Stoughton would probably be a good place to start.
2. Failing that, Fleetguard is in Cookeville, TN.
3. Ryder Fleet Products has a very large product line and can get Nelson items.
A few calls should give you the information you need.
Bob (Squidly Down Under) & Peg - 2013 Ford Focus pushing a 2011 Phoenix Cruiser 2552S
"In God we trust" to preserve our country and bring our Troops safely home.
Carry on, regardless..................