The wing caps are actually a total of 1 1/4" tall, with a 1 3/4" round I.D. for the insert part of the cap that is 1" long.So 1" goes inside the leg tubing and the base piece is just under 2" round on the outside(1/4" exposed). Not really a flat piece.
Any machine shop could cut you new ones out of some bad azz high tech plastic.Be sure to have an extra set cut for your spare parts box.
Build a relationship with a machine shop and they can help you maintain your catamaran.I have repaired some Hobie 18 wing legs with parts custom cut at my local shop and they did a great job on the inserts that beefed up the stressed out tubing without trimming off the lower 3/4" of the leg tubing that was falling apart.I did use an aluminum epoxy like product to fill in the missing aluminum.This two part epoxy is designed to be use on airplanes and my buddy swears by it.He builds helicopters in his spare time....
Good luck,Bill 404 21SE