[Dwight]

you stated you need wider seats. I take it you have seats. Are they the fiberglass units?
If so can't you cut them into and glass them back together?

Local shop I hung around modified seats for "big guys" who like to drag race.
Fiberglass seat; they would cut into, pop rivet a piece of metal to hold the seat apart for the width they wanted. Glass in the gap. Let dry them remove the pop rivets and metal. Make a new seat cover.

Metal seats; cut into and weld in a piece of metal. Most of these were aluminum seat with no seat cover.

Not as easy as buying off the shelf but if you can't find want you want, make your own.

I watched them cut a carbon fiber Pro Mod body into to make it wider. Used the same method. Must work because the car ran way over 200 mph.
Dwight