Made By Hand in the USA | From the Rossville Works
The WE 300B has been made available, don't know for how long. Its hand made in the USA so it's expensive.
They have been manufacturing the 300B since 1997. They moved the manufacturing location several times.
Read history starting at 1997 or read the whole thing:
https://www.westernelectric.com/company-historyBack in the day, in the Bell Labs location where I worked, the stockroom had various vacuum tubes available. Never checked for 300-types, but still have a stash of NOS WECo 417A's.