Thanks Kaiser! These could be what we've been looking for.
Only concern I have now is one I hadn't thought of before - will these fit under the Bakflip? I think they may be too tall?
Edit:
Looks like they'll fit.
I have 20.5" of clear height from top of Bedrug to underside of lowest part of the Bakflip.
Here's what I found online:
SCEPTER MILITARY SPEC FUEL CANS (MFC)
Scepter's military fuel cans (MFC) are manufactured from extra tough, high molecular weight, high-density polyethylene.
The Scepter MFC fuel can exceeds the United Nations - Transport of Dangerous Goods Model Regulations and is Design Registered with Transport Canada, permitting its use universally for the transportation of fuels by all modes - air, sea, rail and road.
They feature seamless construction that is guaranteed never to leak and three integral handles and the flat rectangular shape of the old steel jerry cans that it replaced.
In military live-fire tests, the MFC melts and burns, but it does not explode.
Features/Specs:
Extra tough, Lightweight seamless plastic construction
Easy-open twist cap and built in internal air vent for vapor expansion
Three top handles permit carrying by two people
Flat rectangular shape fits most off-road jerry can racks
Will Not Rust, Crush or bend and it does not rattle
Designed not to explode when engulfed in a fire, unlike metal cans
Dimensions: 18.5'' x 14.5'' x 7''
Capacity: 20 Liters / 5.28 Gallons
Empty Weight: 6.6LB
Meets DOT Regulations
Military Specifications (MIL-C-53109) Approved
http://www.offroadtuff.com/scepter.htm