I figured I might as well throw it out there....
Here is a system that give you a modular mount for a 2 liter fuel bottle:
SW-MOTECH Quick-Lock Base Plate
- Mounts to any flat surface and gives you the ability to remove the holder from your case when not in use.
SW-Motech Quick-Lock Fuel Canister Accessory Mount For TraX Alu-BOX Cases
- Includes everything in this picture plus a pouring spout.
- Base Plate
- Fuel Bottle and Carrier