You can make your own very servicable mandrels out of threaded rod and a couple of nuts, just use the right size drill bit to drill the hole in the insert for the size rod you use, which in turn is determined byut the size of the blank where the reel seat will be mounted. The bit I use is C1215 from Grizzly, I just made a big plastic base plate for an old flat head Black and Decker router I've had forever, it will stand on it's head on the workbech so I don't even need a router tabel A small board and a couple of spring clamps make a fence and another threaded rod with a block of wood on either end make a fixture to rout the mortice, it takes some adjustment and some practice inserts to get it set right.
john