I needed a couple of seats and the rusty/broken expensive offers were not acceptable. Instead I bought 2 ''sports'' seats from a girl whose parents owned a pig farm in darkest Spain. She wanted 300 euros but after I had I smelt them I gave her 100 euros and we parted friends.
I stripped them; cut them to the Lotus bulkhead profile; welded them: had them upholstered.
I insisted that they had more cushion filling than the usual Lotus seat, knowing how hard the suspension can be, and the 'tapiceria' (upholsterer) made an excellent job of reconstructing the seats for 400 euros for the two.
This is the way to go!