Main dealers used to sell Wurth branded items just like this, but most have now switched to the holders with a border which allow the plate to be secured without double sided tape, and are often branded.
I used to prefer these too. They offer a much cleaner look.
2003 W209 CLK, 2005 R171 SLK, Volvo XC40 P8 Twin Motor Pro EV
I have some almost identical to yours. They came from MB Newcastle via their eBay shop. Try a search for "number plate plinth". If it doesn't pop up just get in touch with them and they will put one up for you.
Plate holder just might not fit in the space provided
I like your reg plaste . Would change my reg plate , but its original, it came from the dealers with their name on it back in 1989 .