What you saw seems to be the going prices for Halon or Halitron extinguishers. I bought a 5 lb. Halitron bottle from a place called Harrell Medical in Washington State for $140 and change. Bigger than I really wanted, but after the nylon
oil gauge line split and sent
oil all over the headers (with attendant HUGE f**king fireball)
I figgered it was probably for the better. I do think they have a smaller one for about $115 or so - search for Harrell Medical on Google or whatever. Quick delivery too - took about 3 days. Be aware, however, that halon has been out of production since about 1999 or so - but it seems Halitron is its replacement. Hope to hell I never have to find out how good it is.
