Get these magnets. They are super strong and will solve your problem. Their pretty cheap and work great.
https://www.ebay.com/itm/18-of-1-2-x-1-32-Strong-Thin-Disc-Magnets-NdFeB-Neodymium-Rare-Earth-/381084835248?hash=item58ba6d1db0:g:jssAAOxyOlhSrjgt
I bought these not too long ago for my Dr. Doom PF. The magnets on his head and arm are pretty weak and I easily had enough room for these magnets to fit. Now, everything is nice and tight.