I have a nite tritium glowring attached to every flashlight I own. Got them years ago from a source no longer selling to the U.S. They're great. I can find my flashlight in the dark.. and with it find anything else. I do have one on my keychain, too.

So, I love them. But you can't get them in the U.S. or shipped to the U.S., legally, period. The last I heard some UK novelty shops still had them. They do not trigger attention coming back to U.S. thru TSA, but may trigger attention in the mail. You take your chances.

A friend inquired about obtaining a legal import license, and there seems to be no way the regulation is going to be lifted: it just has too much tritium for a "novelty item".