looking for threading options on battery mod

[OddBeings]

Hi so im trying to figure out a battery mod i want to build, i dont really have access to cnc stuff or any of that but i can do easy stuff like threading tubes etc.. however therein lies the problem, i want to have a stainless steel tube with a sleeve around it but would still like the overall size to be 22mm with the sleeve, id like to be able to buy top caps and buttons etc.. but the inner stainless tube would need to be smaller than 22mm obviously, like maybe 20mm or so, so my question is basically what threading/top cap/button combos if any will work on that size tube but still have easily accessible parts like the buttons and top caps in 22mm but with smaller threading that will fit inside a 20mm or so tube? i hope i was clear enough to understand, please gimme some ideas/suggestions thanks!