Use a worn-out 3/8" drill bit, and cut a piece off the drive shank with a cutoff wheel in a die grinder or a small angle grinder. If it's a press fit, you're in business. A close slip fit can be tightened up by hammering one end of the pin a little bit oval, and adding some red LocTite to the assembly. The drill rod isn't hardened as much on the shank end so it's tough, but not brittle like the cutting edges.
Jerry
