I'll second what Guy says, call some fire extinguisher companies.

Do not use your local welding shop. Did that once and they beat the snot out
of a previously new looking aluminum bottle. With a composite bottle it
might be much worse as they don't want to get bonked. Welding supply shops
typically do not do their own testing, instead ship a bunch of bottles to a
test facility. Probably the shipping to and from where the damage is most
likely.

bumper
wrote in message
...
I get my bottles hydrotested at a fire extinguisher business. Next
day turn around at several places.