I got mine soldered by kriscables.com. It was not fully built, the build service only includes soldering, so I had to assemble parts, but that was a relatively low-skill endeavor.

There are other vendors that offer similar services, and a bunch of etsy listings that offer pre-soldered lily58's. That being said, this will be relatively expensive, a barebones board (PCB + components + case + microcontrollers + labor) without switches, keycaps and cables will cost you like $200 at the very least.