I'm not up on the latest here, I'm thinking of converting a couple of old 2-D M*glites to something a little more useful, like the Firefly PR drop-in and I'd was thinking of an adapter to use one 18650 since I have plenty of them, they are fine for my use and a little safer in single cell config. But I don't see them at Lumencraft. Does someone make a decent adapter tube at reasonable cost? I'd rather not do Aliexpress and the like. Or do folks just use plastic pipe or somesuch?