[Danke]

I don't think anyone will be building a Nuke out of flashlight vials, but if you had an old surplus device out the USSR that's gone stale (I smell a scenario)? The folks at customs seize things like capacitors and other unexpected odds and ends as weapons components. Enough radiological material will get a closer looking at and mess with the rest of your imports.

For the sight itself the biggest concern would be the robustness of the body. If you cracked the lens or vial would you also release the gas? Out doors that would not be a big deal, but it could be serious indoors.