A simple Google image search for "sandplay singing of the dragon gakupo" turns up two different companies selling boots for this costume, so I don't think it would be necessary to have them custom made.
You could also make yourself boot covers if you're unhappy with the boots being sold currently. That would be much cheaper, and there are a ton of tutorials out there to help you make them.
And to answer your question instead of giving alternative advice, I've never heard of a cosplay commissioner who does actual cobbling. You'd almost definitely have to turn to a professional shoemaker.
