Soss hinges have been the gold standard for hidden hinges since they were making them out of brass in the USA. Still, even with the advent of Chinese manufacturing they still are the gold-ish standard. You can buy yourself a pair on Amazon or if you are lucky on Ebay at a far better price. After that you are left with one question, buy or make a jig to install. I vote the latter, but will add a link for the jig the provide if you want to take that route.
And for those of you who would like to know more about the man who invented the hinge in question, here is a link about his life, and what a life it was!
I have added the files that I used for my bushing and router combination. The sizes will likely need some tweaking based on your own tooling.
