Tung-Sol is the only manufacturer that makes the KT-150 and the KT-120. It will not be easy getting these or any other Russian made tubes. I have used the JJ KT88 tubes with my QS amps. Take a look and you will see that the Russian tubes are not available!
https://www.tubedepot.com/t/tubes/power-tubes/6550-kt88-kt90