Lotus S1 Warranty

[Mr Overheads]

I'm about to list my Yellow S1 for sale and given it's been 100% reliable was looking to get a 3 month or 6 month warranty and throw it into the deal for whoever buys it, just to try and set my listing apart. However as it's 1998 I can't find any of the Warranty companies that cover cars that old. Has anyone managed to buy a warranty for an S1?