How to add magnets to Con-bought Buster Sword?

Hey all! Hope this is a good place to start this endeavor, as I've never worked in cosplay or any of the materials before.

I recently went to my first Comicon and bought a pretty sweet looking Buster Sword!
(not to proper scale, but close enough, and the weathered paint job on it looks awesome.)

I want to add magnets to it so I can mount it on my back like Cloud holsters it in-game. I've seen lots of examples of other cosplayers achieving this, but they all are building their swords from scratch, so they can layer in the magnets during the build.

I found some good magnet recommendations on another post (looking at something like 1 3/4 W x 1/2 thick Inch Neodymium Rare Earth Disc Magnets N42 rated for 84lbs each; I'll probably get 4 magnets - 2 for the sword and 2 for the back strap [a problem to be solved later])

My question is: What would be the best way to add these magnets to the sword?
My initial thoughts are to bore out two 1 3/4" x 1/2" holes in one side of the sword with a spade drill bit so I can sink the magnets into the material and then paint over them, but I'm not sure how to properly mount them so they don't get pulled back out of the sword after repeated pulls against the strap.

I reached out to the vendor about the sword material, and they said "it's a high impact foam with a fiberglass insert". Is there a certain kind of glue I can use that will bond well between the metal magnets and foam sword? Maybe use a thin layer of EVA(?) foam to cover over the magnets to help them hold as well? Or do I need to figure out some kind of mechanical way to fasten them into the foam?

Any insight or advice would be greatly appreciated, cuz I really want to stick this thing on my back!