Was looking for an alternative to the $10 magnetic key chains I could find on the interwebs. Took some inspiration from That3DPrintGuy and his take on it. (https://www.thingiverse.com/thing:672357)
Was easier to just jump in TinkerCAD and make it from scratch than to modify any existing files. Have two files, one for 6mm x 3mm and one for 8mm x 3mm magnets as that's what I had handy.
The author hasn't provided the model origin yet.