There are multiple Thai tailors that fly around to major US cities. They'll take your measurements, and then sit down and design a bunch of custom clothes for you.
Quality is amazing, fit is incredible, and the price is only 20-30% more than off the rack, but the clothes can last a decade+.
Sometimes the ancient solution (meet another person with a measuring tape) is the best one.
What is the ballpark, 20%-30% of a $20 shirt, or 20%-30% of a $200 shirt?
You can also get a local tailor to take your measurements and then order direct from tailors in Thailand or Singapore, and it tends to be cheaper than off the rack.