You know, without photos, it's kind of hard to tell what your up against. But, if what I am reading is correct, The flange on the converter is broken free, correct?
What I might try, is find a muffler shop, and proabaly not the big ones like Midas. See if they have a flange from a removed converter or what have you that is the same size that you need, and have they weld it in place. They weld this stuff all day long and have the tools and knowledge on how to do it. You might have to go to a couple of them., but it might be worth a shot.
Greetings, Earthling. We come in peace... Never mind "Paris to Dakar", the VehiCROSS looks ready for the Martian desert.