Personally I use two kinds. I use the factory Autolite ones on my own cars because they are correct and easy to set using factory shims. They are very expensive these days, good thing I have new spares in the box that I bought years ago. No they are not for sale.
The other ones that are easy to adjust are made by Crane. You can buy them at Summit, Jeg’s, any place that sells high performance parts. They don’t look original but they have an allen wrench adjustment for the advance which is very easy to adjust. They come wildly out of adjustment when you buy them. They cost something like $50.