You're asking the wrong questions. You won't find some magical place with loads of pristine restored III's. You need to know what exactly it is you're looking for, especially if you're prepared to pay a premium for a nice example.
What's your budget? Have you driven one before? - If not, I would, it's a culture shock! What do you want it for? - Occasional greenlaning, everyday transport, towing a trailer full of pigs?
Try a search on here for 'buying advice' things like that, there's been a lot of similar posts.