You're not one of the few, or if you are, I'm one of the few, too. I've considerably more formal wear than that, but most of it is second-hand, some of it is EBay, and it's slowly accumulated over a period of years.

I re-rigged one of their Eton jackets with 5/8" gilt "Erin Go Bragh" harp buttons and a chain, similar to a mess jacket.