I ran into the same issue you did. The right side mat did not exist in the aftermarket, black or gray. What I did was to sacrifice a new center mat and cut it up into correctly sized pieces. I made it into a group project and polled to see if any others were interested. Based on the number of interested people, that is how many large mats I bought and cut. Then I just took the cost of the mats and divided into the number of participants to get the unit cost.
I didn't make any money on it, but I got the mat I needed and helped others along the way. Can't do much better than that. I did not have the correct right mat for mine and a member of another forum graciously took dimensions and sent me a template of his. From there, I matched it to my car for accuracy. Easy to do and just requires a bit of effort. And yes, the color match is very good and only imperceptibly different. My main mat set and the right mat came from different sources btw.
I believe there have been similar projects to this on SL113 and the firewall pad comes to my mind. It shouldn't be hard to do the same.