Where to weld exhaust possible?

Hello, I have found /no/ suitable forum area, therefore here. I have a crack on 2 exhaust pots at a weld seam. In a few months I have TüV. A pot would cost /500/ Euro that times 2 :-))) I would like to have the seam welded. Not by a forest and meadow man but by one of the masters. Does anyone have an idea where I could find such a welder? Could I ask at a workshop of another group? Do the group workshops or verka Are the only new exhausts available? Would that make a free workshop or not all? Would that be welded with protective gas or with gas? If the exhaust would be removed and installed, what could that cost? Thank you.