WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
We don't have any such speciality shops indeed, although there are many audio enthusiasts over here for sure. I used to buy ex-military tubes, PIO, Teflon and silver mica capacitors at eBay from Russian vendors.