The only realOEM things I could find are the parts that I used, which are felt covered plastic insulation units, which cost about $36/each. These aluminium covers are designed to cover them. I cannot find bespoke metal/plastic skid plates for an E90 M3. That is why I built these in the first place, as I believe I am doomed to destroy more with the lowered car and the angle of my driveway relative to the road. I also wanted to make sure that the leading edge had some cover, as this was where the original parts abraded, rather than cover just the bottom of the section.
For a couple extra hours work, and I had to replace the parts anyway, it was worthwhile. (I think)