I switched to tailored shirts a year ago and it is absolutely true that it would be almost impossible to switch back. Shirts that I thought to fit great before, now just don't cut it.
I use modern tailor (moderntailor.com) website and so far it worked out great. Shirts are very well made. I've had few issues with the material - living in Houston, few shirts I ordered were just too heavy, but after few tries you learn your way around swatches and materials.
For the first shirt, you should plan it to be a test, so get something cheap.
One thing I would like to try, but it is just too expensive to test the fit, is to buy the pants. For those, I might find somebody in Houston that can tailor it locally.