Here is a link and information that I found

https://www.oilfilter-crossreference.com/convert/K-N/KN-204

I know this reply is a bit "late to the party" but I tried one of my RZR seats on the 2013 z6 and it indeed is too big.  Front pegs don't fully slot into the brackets and the lock hole is not in line with the rod on the frame.  Good luck in finding a seat though.

NOT TO GET OFF TRACK but..... I was wondering since you own a RZR and a Z6 I'm looking to replace my bottom seat cover because it is torn and the only (vinyl) covers I could find is for the  RZR replacements
eBay has them for $45- $60 but I'm not sure they will fit. Any help would be greatly appreciated.