So I was going to get all precise and get an exact size mouse pad to go up against my keyboard and table side but I thought "fuck it, I'll just get a massive mouse pad for my mouse and keyboard, seen them before so yeh".
So where would I want to go to find a good quality mouse pad that's 750mm x 300mm give or take 5cm. (no less than 300mm deep though).
That looks about right actually, it's a bit too big in both width and depths but I could make it work, how ever if there's one that's about 100mm shorter on both side that would be perfect.
The Corsair MM200 is less deep, but about as wide. You might be able to get one of these and cut it to size, if you're able to seal the cut so it doesn't unravel. I don't think I've seen a mat the exact size you're looking for tho.