You might take the old tubes and soak them in helium
gas for a week or so. If their seals are in tact, that will
replace the He that leaks out over time. Get one of those
metalized-Mylar balloons and put the tubes inside, fill
with He gas and let it sit.

This was a problem with the original LaserDisc players.

By the way, at least one expert is predicting that, because we're using so
much helium for trivial purposes, in 50 years or so we won't have any for
scientific use.