Should always keep Mud Hole on the top of the list for anything Rod building related.
http://www.mudhole.com/Shop-Our-Cata...e-Cutting-Grit
But I would also take a look at these grit-tape products. Much easier to make a reamer out of then by using lose grit. At least easier to make a consistent shaped reamer
http://www.jannsnetcraft.com/rod-bui...550200007.aspx
http://www.mudhole.com/Shop-Our-Cata...sive-25ft-Roll