Thank you again for all your efforts. At least your bracket is clean now

I just sand blasted mine and powder coated black. The clamp - well, I will have to live with zip tie style fitting. I'll make it somehow...
BTW this sort of fastening (press in pin style) looks to me identical to some '80 Porsche style fittings. If you want to remove it you have to press the pin from the bottom out, not inside in. Unless you have already tried this way...