Well, that’s a tough one. Bears have become an enormous problem in the Sierra, regularly getting their mitts even on food that is hung in an “approved” fashion. And you’re right, some National Parks are not allowing the use of Ursacks, a super-tough bag designed to be tied to a tree. The bear can smell the Ursack, and get to the Ursack, but not open the Ursack. Ursacks ($70 for a 650-cubic-inch bag) generally seem like a good alternative to other bear-proofing measure, as they’re relatively light and can be compacted once empty.
So, a titanium canister would seem to be the answer. But….there is no such thing. As common as titanium has become these days, it’s still a pretty expensive metal, so a whole bucket made out of the stuff likely would cost $500 or more. Plus, it can’t be cast like most metals, nor can a canister be machined out in a cost-effective manner. So it’s just not in the cards. In lieu of such an exotic device, you’re left with traditional bear canisters such as Garcia Bear-Resistant Container ($78), which holds up to six days’ worth of food if you pack with excruciating care and use foods such as rice that yield a lot of volume when cooked. Made of ABS plastic, the Garcia container weighs a little less than three pounds, so in itself it’s kind of a load.
My only advice is to figure out a way to pack a wire and a slingshot. Use the wire to rig a hanging device as high as possible, then the slingshot to sling a weighted line over it. Make the best bear-proofing device you can, be cautious with your food, and hope for the best.