911/993/964 Cup holder options:

Porsche Dealer Offering

Sleepers Speedshop Cup Holder 
https://sleepers-speed-shop.shoplightspeed.com/sleepers-cup-holder.html

Fast-Ind two cup Offering

Rennline Adjustable Seat Mounted Cup Holder 

https://www.rennline.com/rennline-seat-mounted-adjustable-cup-holder-sku-sa05-06/

CNC ALUMINUM CUP HOLDER
https://www.autoatlanta.com/Cnc-Aluminum-Cup-Holder-For-Porsche-911-1965-98-Parts-PN-RAIR1.html

magnetic-seat-rail style 
https://classicmotorshop.com/products/cupholder-porsche-modelle-1980-1996

Rinashi cupholder 
https://i0.wp.com/rinashi.com/wp-content/uploads/2023/02/DSC08179_optimized_250-e1720027992462.jpg?fit=750%2C420&ssl=1

Amazon offering.
https://www.amazon.com/s?k=porsche+993+cup+holder+insert

Prestige Parts Center Console Cup Holder
https://www.pelicanparts.com/More_Info/PELCH964.htm