This is going to get old explaining to people lol..... The BBS E26 Motorsport wheels weren't intended/made to accept center caps. They're true motorsport wheels originally sold to race teams that either came in a specified lug pattern or center lock. I may try and have some made like the others you might find out there, but that's not really OE equipment for these wheels, and would stick out like a sore thumb for anyone who is aware.
No intention of clear turns, either. The amber and purple go great together and I have a fondness of the little bumperettes people usually get rid of.