So I really don't think they are painted. I am going to take s fine grit sandpaper and see if I can rough it up a little. If not, I'm sure these can still be found brand new online. They made hundreds of thousands of SLKs and I'm sure the breather covers are still around.
Maybe even purchase a used one and have the breathers and valve covers coated so this won't happen. That's a great tip.

I just didn't feel like re-sealing as the SRT w/25,000 miles doesn't have any oil leak issues.

My 130,000 mile NA Coupe had no imperfections on the covers. But I guess it can happen and it is just old age.