And here's a guide for anyone to make their own with some spare MX stems
Things you need:
Dremel (or something for cutting)
Epoxy (I used superglue, epoxy would be better)
5mm x 1.5mm magnets (I used 3x1mm, they can hold up a keycap, but just barely)
MX Stems
Start with a MX stem
Shave off the "legs"
Flatten the area for the magnet to stick
Like I said, if I'd do it again, 5mm magnets and epoxy
Stuck pretty easily
Fits perfectly
Yey!