Are you looking for someone who can *design* one? Or someone who can make one out of material of your choice? There are lots of people who can follow a pattern and make an article of clothing but couldn't design one from scratch. I wonder if you're asking the right question when you approach people. If you came up to me and said you wanted something designed, I couldn't help you. But if you handed me a pattern and asked if i could make one - I can do that and so can lots of people.

If you have a crafting store in your area that sells fabric, patterns and sewing machines try in there. Tell the staff that you need something made and I'll bet you'll easily find someone who will do it. One of the chain stores here has lessons you can sign up for. Someone in the class might need a project - or go crazy, and see if the staff at the store can show you how ot make something from a pattern. It's fun and not terribly hard.