Prob best to contact a dealer or GW via the customer service link. I don't believe it changed all that much over the years. There was a rubber version and later a version with a stainless steel insert.
If that doesn't work, I'd go to a GW dealer or local marina and measure them out and take some pictures - specifically seeking size, picture to start a web search and manufacturers to start to inquire. Maybe do this first, so you can use in your conversation with GW or a dealer. I'm sure it can be defined and obtained, just will take some digging and persistance.