I fabbed up a seat for Goldie. I had an old piece of 1/8" thick aluminum, so I cut that out as the base. Then I added two pieces of 1/8" thick 1"x1" aluminum angle that act as both the hinge point, and add some structure. A pair of rubber bottle stoppers hold the seat against the fuel tank.
Bottom side of seat pan:
I had some leftover fabric from El Guapo, and thought the brown would work great with the gold/green color scheme. Three layers of foam and a couple layers of batting provide the cushion, while a few "furniture movers" push through to give the tuck and roll look.
I also made up some side covers in card stock, to get the right shape and size.