I... don't think there are any fluid canisters in the labyrinth. There was a part there, yes, maybe some sort of valve or shaft (which your character inserted), but not a canister.
If, in light of that information, you want to explore some more, go ahead. If not (certainly understandable), here are spoilers about two more canisters you can get:
One is guarded by a lot of burrowers, as well as burrower warriors, near an elevator. The other is in the Tchortist base, behind the electronic lock. I know that destroying the Faceless base in Talos Outpost and rescuing the Tchortist hostages there will result in Harmost Stavros giving you access to that canister. I'm not sure if it's possible to negotiate their release with the Faceless if you are friendly to them, or if it's possible to get past that electronic lock in any way other than doing the quest. Obviously, most characters would find getting the one near the burrowers easier.