Hello Gil,
As an early-230-aficionado owning 2 (poor) pairs of the early-style seats (seat type 1, up to serial 002926) I should know about your question or shoud have pics.
But I don't.
Well...,
I remember faintly how the leaf spring frame of the seat cushion looked like before I sent my (late) '64 seat cushions (seat type 2) out for renovation.
To make a short story long, it "should" be possible to convert a later seat cushion (all seat cushions frames after 002927 are identical until the last 280 SL) but there is then in your case some replacement of the outer flat leaf springs necessary. And I think this is definitely a job where only an experienced shop can really be of help.
Surely you could cut and weld something there .... but it is made of spring steel and that really weakens if welded ....
No good idea, I think.
Currently I do not have pictures what I am talking about ....
maybe Andy (Andyburns) has some since he has also the early seat type 1 and I remember him having trouble to obtain the correct seat covers from GAHH as well.
Contact him here via PN.
Good luck !
Achim