Easiest solutions are the new BEAR PROOF coolers out by both YETI
www.yeticoolers.com (tundra series only)
http://www.alltackle.com/yeti_fish_coolers.htm and Engel
www.engel-usa.com . These companies have developed much higher tech coolers that can keep icey for up to 10 days at a time. ARE lockable and approved by the various Grizzly Bear agencies.
These are on the pricey side. $240 roughly for 45liter versions......but the insulations are much better than the old school coleman coolers and food stays cool 7-10days.
Getting your door ripped off.......small child mistaken for a snickers bar........dog gobbled up...........makes these high-tech items seem like a bargain after the fact.
ALSO- only "on the beaten path" parks have bear proof boxes.......and if you do any sort of boondocking in the wilderness or off the beaten path.....bear boxes and campgrounds are not an option and your children, dogs and spouses are all "snacks" to those higher up the food chain.
Another option- and one i currently have for dry food is from----
http://www.bear-aware.com/newproducts.htm. Aluminum and very beefy construction. They do custom versions and i plan on having one that fits a 45l arb fridge..........mounting it to my rear swingout carrier--and drilling a hole thru swingout-box-to power fridge from inside vehicle...........FULLY Bearproof--unless he can figure out how to rip off my 3500lb swingout spindle thats welded to 3/16" plate steel.
http://bearcountrycamping.com/catalog.html - these seem well built as well and he also does custom sizing. The main glitch will be the 12v cord.........a bear will rip that easy- and the hole for the power cord---unless not exposed---will act as an entry/leverage point for the bears claws.
ONE unforseen problem with all coolers.....is that bears tend to pick up and run with stuff........miles actually. I had a coleman last year that got clawed open- and the bear was able to take it 1/4mi into the heavy brush to dine. A good solution for any of these aluminum boxes would be having a thick padlock tab welded on and then lashing it with some heavy kryptonite sized bike chain to a tree or camp table.