Looking at it, I think you might get lucky and your flashlight will fit the same tail cap magnet as the smaller A series.
https://www.rovyvon.com/products/ra30-magnetic-tail-base
If not, neodymium magnets come in lots of shapes and the strongest glue that doesn’t eat plastic
EDIT: nevermind I see yours doesn’t have the little ridges, would have to file yours a little at a minimum and do real measurements.
You’d think they’d standardize them since $6 for that little thing probably has huge margin!