Arlington Industries ( www.AIFittings.com
) has some good stuff for landscape lighting solutions. All of their stuff is made of PVC, so I can't attest to the fact that it is "bear proof".
I've run into similar situations, but not due to bears. It was more due to errant lawn care people at a country club. We ended up putting support stubs of 2" RMC embedded in concrete with sufficient reducers to thread into a 3/4" outlet in the box with an 18" section of RMC. In our situation, everything was fed by UF cable, so we just dropped down out of the second hole on the box with a 12" RMC nipple and appropriate end fitting. They still get hit by lawn mowers and bent, but rarely broken. Even if they are, we still have that solid base of the 2" RMC about two feet down that we can thread a new nipple into with minimal effort. The job was very expensive to do, but the customer was spending more in one year for repairs than we charged them to do it correctly.
In most cases, the UF was too short, so we just dug back about two feet to gain slack on the feed end of the cable so that it reached into the box. We then relocated the fixture location slightly in that direction, which was barely noticed. The outgoing cable was spliced using T&B buried splice kits, but we left a tag inside the box indicating exactly where the splice was with regard to the box.
John, I'm not sure where in NC the original poster is, but the western part of the state is quite mountainous and had a good-sized bear population. They are showing up in densely-populated neighborhoods all over the place around here in Virginia. They must be hungry.