The photos you referenced are of a Van Specialties van. I believe those are Atwood brackets. I also think that FWC may be the cheapest place to get them, as Van Specialties will probably want to sell you the entire seat. On my FWC Hawk Front Dinette, they used two of those brackets for the dinette. The actual seat part of the dinette was simply 3/4" ply covered with foam/fabric, then bolted to the bracket.