On ebay from Duncan I bought a used key for one of my sidecases...key is no longer produced and I had the part number as a saved search for over a year. I was bored one day and was searching for the code itself and I happened to find his listing.
Anyway, I also received this from him:

Since I don't have an airhead, and I don't exactly know what this is, I'd be happy to put it in an envelope and send it to anyone who needs it FOR FREE.
Is it Duncan's thing to send everyone a complimentary seat button latch cap? At least that's what the handwriting looks like.