If you have a flat top battery that "needs" to identify as a button top, there are neodymium magnets in many sizes that can be applied to the positive cap thus rendering the profile to more buttony.
Hunt diligently, and purchase a variety of thicknesses and diameters and you'll be well on the way to finding the ultimate fit.
This works for all
mods. I have used one for years in my Ohman Microstick, a Ti single 14500 mech
mod with no adjustablility (other than leaving the tailcap partially unscrewed, which in my eyes is hideous).
And then also, you'll have a load of really strong, small magnets suitable for a multitude of applications involving ferromagnetic surfaces.
Here's a handy link to a magnet
shop, helpfully directed to their page of neodymium disc magnets in a variety of sizes:
Magnetsssss