I use jlcpcb, they're common in the prototype and hobby domains. But there's quite a few board houses in taiwan and china that do this, definitely shop around.

The annoying part is getting the bom and component placement files correct. I use kicad since it's free, and there's solid instructions from most houses on what they need.

JLBPCB does small runs cheap as a loss leader, so they get the production runs, if any, later. Also, they get to see what people are doing, in case something interesting goes by.

There's also a suspicion that JLBPCB may be encouraged to do this by the Party, to discourage other countries from maintaining an independent prototyping capability.