Excel Sports Boulder builds frames to order, although you'll pay more than if you buy the group from an online UK retailer and assemble yourself. I spent $2200 doing that in 1997 with a Litespeed titanium frame, Look carbon fork, and Campagnolo Chorus/Racing-T/Athena mix. Obviously I got exactly the gearing, wheels, saddle, bar, tires, tape, etc. I wanted. With inflation that sort of thing will run at least $3500 today.
Small builders will also work with you.