How To Replace Kohler Rialto Toilet Seat We Need A New Toilet Seat For Our K3402 PB 1071 Please Advise Which Can Replace The Old One?

We need a new toilet seat for our K3402 PB 1071 please advise which can replace the old one? - how to replace kohler rialto toilet seat

I think our bathroom is one of the Rialto Kohler bought about 1983/85 in chocolate brown. His head needs to be replaced and does not know which model is suitable. Can you advise me? Thank you in advance. Regards