7 gallon plastic jugs can be found at Walmart (short and square) for $11 or Kmart for $9 (tall and narrow like a metal jerry can). Both have a carryhandle, rubber seal, and wide mouth cap with an integrated spigot.
Six months ago I found new 55 gallon blue plastic drums with a rubber seal, very wide cap, and brass spigot threaded for garden hose for $50 at Orscheln's Farm and Home. Also fairly clean, used 55 gallon drums with two small bung holes for $20. They have a shitton of locations in Missouri:
Map
I found you can get new 55 gallon water tanks made from a more rigid plastic from Rural King, but you're looking at $100 or so. For that matter, you can get everything up to a fairly huge 2000 gallon plastic water tank from Rural King, but it ain't cheap ($800).
On second thought, that's not bad per gallon.