You need to find a good local bike shop. I deal with one close to my home and another close to my work . Either would be more than willing to build up anything I request and also help out with selecting components. If the shops you are visiting can’t provide this service I suggest you keep looking for one or two that will.
There are a number of online shops that provide this service also. I’ll include the links.
Happy shopping.
https://www.speedgoat.com/ check out the bike lab
https://www.excelsports.com
www.coloradocyclist.com