I have one, an I3 slim that is at Back Roads Gold being replated with nickel as we speak! I found it on the bay years ago enough where they were pretty plentiful and cheap.
I have both a Flare Tip and a Red Tip Superspeed in my birth year and quarter - C1, 1st quarter of 1957. I got them both on the bay for fairly cheap. The Flare Tip is in really nice shape, but I haven't used it for several years. The Red Tip I had replated in bright nickel and it's a regular in my rotation. I just searched for Gillette C1 on the bay and was surprised how soon something popped up.
I was also looking for my birth quarter razor, l found and bought a K-2 flair tip with little difficulty on the 'bay last year. I just typed 'Gillette K-2 razor' in the search engine and presto!