I made my own. I don't have the third row, but I just took some rubber matting and cut it to fit with a razor knife. I used an 8 foot 2x4 as the guide to keep my line straight. It's not perfect, but it looks fine and it works great.
The mat was from a farm/feed store. I think its used for animal stalls or something. One side had large dimples, the other had ridged lines.