Yeah, I'd figure a shortened "special" load... Run the head up too, so you have a long tunnel for the primer... Drop a little powder, crimp in a round ball, call it good.
Worse comes to worse, I can probably make a bullet mold, but I'd rather not jack around with that - too much like work.
(mold makers think upside-down and backwards - wildest thing the shop did was a setup for injection molding shot cups for a 16 gauge run...)