How old is the unit? In some cases if the unit is over 15 yrs it may no longer be available. Without a model and serial it will be guessing game. Call 844-411-8050 for Perlick tech support. Hope this helps!
Another option is to simply have the gaskets made. We’ve used GasketsUnlimited.net a few times and had great success. Call them to set up an account and get instructions on how to determine your measurements and style of gasket you’re looking for. Their prices are EXTREMELY reasonable.