I know everyone is into the MSR fuel bottles to carry extra fuel. I found aluminum water bottles in a variety of sizes at my local TJMaxx, for about $7 each. I picked up a .6l in red that I'm going to stencil the word gas on the side with yellow spray paint. the plastic cap is #4 plastic the same as my gas can and it has a silicone seal to make it water tight.
Thought I'd let every know as it's a pretty good deal on the metal water bottle and cheaper than the MSR bottle