there's an outfit called
Dynacron [wholesale only] that's making a slew of new sheet metal - including complete door shells and front fenders for the task force trucks [check the truck parts 'catalog' - great stuff]. takes major money as well as major equipment to make body patches, let alone whole fenders or doors, so there's not many places doin it, tho' there's one other US outfit called
Goodmark that makes a lot of good patch panels and major parts.
Bill