If you've ever wanted to make your own seat but think you can't, you're dead fucking wrong. You don't even have to know how to sew! I found an old-world leather shoe craftsman in my area and he does awesome work. He runs all of my seats through his industrial sewing machines for $20-35 bucks, depending on the size.
The leather I get at the local Tandy Leather, usually for around $35. The dye is about $8 and the glue is about $10. The foam is whatever you have available, but I like old pool floaties, yoga and camping mats from Walmart for $10.
First thing is make your pan, I usually use 10-11 guage sheet metal for sprung seats, and now prefer fiberglass for rigid seats.
Lay out your pan and cover it with foam. Shape it how you want. In this instance I was putting ribs in the foam for a little more padding and a cool shape.
Then cut enough leather to cover the bottom of the pan. Push the leather against your hinge and spring studs to know where to cut them out. Then use a punch to cut the holes for the studs to poke through
Cut the leather for the bottom of the pan out, about 1" wider than the seat pan.
Glue that leather to the bottom of the seat pan.
This Super 77 glue wasn't as effective, because it will seperate after a little bit in hot environments. Contact cement does work well however.