Now that I've had success restoring a lamp, I've got a couple of others I want to "fix" as well. But they have bottle caps and the last lamp I fixed that had a bottle cap didn't survive re-sealing. So I was looking for something that could convert a bottle cap to a screw lid and I found these silicone caps called "Beer Savers". My thought was that beer is fizzy so they would have to be able to seal tight enough that they could keep the gas in, so maybe they would work to prevent the lamp water from evaporating or otherwise escaping.
Has anyone tried them? It just feels safer than trying to re-seal the cap with a hose clamp and a whole lot cheaper than investing in a bench capper that I'm only going to use "twice".