If you have other die sets see if the nose plug from one of them sets good on your bullet and screws onto/into your seater die.
A temporary modification to your flat nose plug can be made with a hot-glue gun; clean the plug cavity and bullet nose, smear a little cooking oil on the bullet nose, squirt some hot glue into the plug cavity and center up the bullet into it to harden. Same principle as doing epoxy but it will clean out pretty easy if you use several different bullet types.