As Nassau says, you'll find a much greater choice in the States. If you visit the States you may have to cover a lot of ground to find a car you want, but unless you're prepared to go and check a car out yourself or you know someone over there whose honesty and expertise you trust, you'll be relying on the sellers description or you'll have to pay an unknown agent to inspect the vehicle on your behalf. Remember that your ideal car will be 54 years old but because glassfibre bodywork doesn't rust it may look perfect in pictures. It may take longer to find a car you like over here but at least you'll be able to check it for horrors like birdcage rot before you buy. There are a number of dealers over here who often have good C3's for sale,
Gavin at EMC is one who has a good reputation with the club and is very helpful.
I bought my 1971 350/270 Manual convertible over here five years ago from an individual who'd imported it a couple of years earlier. He'd found it needed a lot of unexpected work that he'd spent considerable money on and that he didn't recoup from me. When I bought it it still needed a lot or work but at least I knew what I was letting myself in for.
It's taken a while and a significant expense to bring the car to the standard I want, but I do now have a presentable and reliable great drive.....
Good luck with your hunt and do remember, it's what's underneath that's important.