The two ideas on paint cans got me thinking (always a dangerous undertaking.) Some paint now comes in plastic gallon "cans" (cube-shaped, with a neat handle and a screw-on lid); I know this because I spent a weekend up close and personal with Sherwin Williams and my wife. It shouldn't weigh much after you remove the drip-guard inside, and the shape is somewhat pack-friendly. Would the screw-on lid pose a problem? (As noted in my post below, I've not been bothered very often by critters, so I don't know.)

If screw-on lids work, what about those gallon-size plastic jars that mayo, ketchup, etc. comes in? Any school cafeteria or fast-food joint probably has tons of them they'd like to get rid of. The shape might even be more conducive to packing.

Just a thought, with absolutely no credible experience behind me.