Searching for Cave Fish and Oxygen in Thailand

[Wayne Harrison]

By WILL GADD
New York Times
Published: July 13, 2006

A lot can be learned about a group of people by the games they play at parties after a few drinks. Financiers may indulge in liar’s poker, retirees perhaps some shuffleboard. Cavers, the intrepid explorers of the wet, cold and pitch-black, have been known to strip naked and try to worm through an adjustable boxlike contraption that simulates squeezing through a small section of cave passage. If a special “squeeze boxâ€

[CKB69]

I don't have to go as far as Thailand for that special hypoxic experience.
Where do they get those cannisters?