>>10063191As an anon who was first turned onto replica, and later, custom sabers by /toy/, you are looking for Custom Saber Shop.
They are an independent outfit in Idaho. They offer everything you need to build a custom saber. There is a creator on their site to design what you have in mind, and they can paint and/or machine pieces to whatever you have in mind, with a customer support staff that I found incredibly helpful. Additionally, they have an informative YT channel with videos demoing and explaining new products you can use, how to make the most of them, as well as others explaining the fundamentals of actually building a custom saber. It was first recommended to me, and as someone who only had a pleasant experience, I can't recommend them enough.