I'd check with Nikon UK. They should be able to order it for you, if they don't have it in stock.
The other possibility is to keep checking eBay. It sometimes does pop up. In fact, a couple months ago, I saw one listed by someone in the UK. Watched it until I realized that the project F5 body had a bad shutter.
I don't why Nikon decided to go with the new rubber material that can come off easily. The leatherette that was on like the Nikon F3 would almost never come off. Besides one can design a camera without any rubber or leatherette like the motor grip on the MD-4. It's not that slippery. Paint does come off but still look a lot nicer than a bad rubber cover.