The Opel Frontera is a rebadged Honda Passport/Isuzu Rodeo; looking for parts for one of these models will be much simpler and yield much better results. Go to a Honda or Isuzu dealer, or to a general 4×4 outfitter and ask for help with a Passport/Rodeo.
you can get a lot of new parts of ebay, but you might have to log onto the uk site to get access to them and see if they will ship to the USA.
Have you tried Summit Racing? I know they have tons of 4×4 accessories, and street as well. I go there for my Jeep.
The Opel Frontera is a rebadged Honda Passport/Isuzu Rodeo; looking for parts for one of these models will be much simpler and yield much better results. Go to a Honda or Isuzu dealer, or to a general 4×4 outfitter and ask for help with a Passport/Rodeo.
Have fun =]