New Bench Rearseat.

Hi. I wonder if anyone out there could point me in the right direction ? I am looking for a bench rearseat to a customized car. So no brand, no replacement and no seatcover.

What I am looking is a backseat with rails to put where there has never been a seat before. Wasted a couple of hours on the internet, all to no avail. Ended up with babyseats, seatcovers and factories in China with minimumorder of 50 pcs. I drive between Hua Hin and Bkk quite often, and along the road there are plenty of stalls/shop with everything for cars, but no seats. A pointer to a company, a webpage would be most appriciated. Thank you.