I had to do exactly this job in steel sheet to make an exhaust system for a project. I went through a box of old hex sockets, found two, one with the right external diameter for the hole, and a larger one it would just fit inside, put them on some threaded rod, and pulled the small socket through the hole into the big one by tightening the nuts, worked like a charm and left the perfect swaged hole. I suppose finding the correct sizes was lucky, but it worked for me! If you have a press and can turn up the tooling, git er done!
Phil