Success!
TJK was right!
I had previously looked under the phone book for fire supply, but today tried "fire extinguishers" and came up with more names.
Most importantly I explained that I didn't need the extinguisher for a home or business, just hobby, so would take a used one. Bingo, that did the trick. A local company is dropping off a 5# aluminum CO2 extinguisher tomorrow. Cost -- $50. Not as cheap as some of you, but I am relatively speaking in the boonies (Maine).
Thanks guys. Now on to a pony scuba tank.
Antony