The Finishing Touch does quality work. I have used them to replate diecast but I believe they also do bumpers.
I've met the owner on a few occasions @ shows and he seems dedicated to quality workmanship. Of course the pricing is in accordance $$. Also be forewarned that they can get busy and at least with the diecast (potmetal) you might wait 6 months for items to be completed - its worth the wait.
http://www.thefinishingtouchinc.com/
CF