I made one using a dremel with a cutoff wheel and a 1-1/8" socket.

Vertical cuts were made freehand from some marks I put on the socket while holding it up to the swingarm lock nut. Horizontal cuts were made with the dremel in a dremel drill press stand and moving the socket around on the bed to make the cuts, though that could be freehanded as well. Final trimming done freehand as I put the socket into the locknut and checked the alignment of the tabs.