There many different back quivers and side models. The each have advantages and disadvantages, depending on what you like.
Personally, I like the Hill style, and I have made or bought the St. Charles, Safari, and CatQuiver. You might start by searching online for quivers sold by custom makers, as advertised in magazines and this website. Collect a few catalogs, like 3Rivers and Kustom King. Find a shop or Trad shooter in your neck of the woods and see what they like for the type of hunting you might do.
A carpenter's rule is measure twice and cut once.