You know what I would do to get high-energy stones, were I to have his powers? I'd practice using my teleportation so that it'd look like I just walked through a wall, then show it off to some big gem store by "walking" through the glass of a display case. I'd claim I was one of several "rift walkers" I knew of, and so there were probably hundreds, if not thousands, of us in the country.
Then, I'd say that some kinds of precious and not-so-precious stones, called "rift stabilizers" by those "in the know" could block my kind of ability, and I'd show that by slamming face-first into a case containing one of the high-energy stones. Then, I'd offer to help them safeguard their store by having them gather similar stones, and I'd tell them which ones would and would not "block" me. In reality, I'd just pocket a few of the high-energy ones, and get them to use the rest to protect their gems.