Just had a thought....
depending on what the drums are made out of , it should say right on the drum, you might get fittings hand- or spin-welded on if you're near a place that does tanks and/or plastics repairs.
And there ARE those fittings that kinda clamp on.....
Some RV catalogs carry the tanks, parts and spin-weld tools in their catalogs; Crossroads RV does, anyway, I'm sure there are others.
I've done plastic welding, you need a steady (fairly large, volume-wise) air source and the welding tool, along with the appropriate plastic welding rods. The welds are just as strong as the original plastic.
Look for a body shop nearby that does plastic body and bumper repairs; also, some motorcycle shops repair plastics (that's what I did), as some bike plastics can run into the BIG Bux !!!
The tool storage is nice, but where do I put the bed?