This looks like the very large 5 gallon( U.K gallon) or 25L plastic tank with a tap dispenser. If I am right then a home-brew shop or mail order would seem to be the best place. Not sure what you want to keep in such a container but if it is developer or fixer I'd be wary of oxidisation especially with developer.
Much better are the wine-bladder in boxes stuff. Google "polypins". These are small to very large bladders in boxes with taps which prevents any oxidisation. The only snag is that I think there is a minimum order quantity but it is worth investigating