I'm sure they could, but sourcing people willing to manufacture heavily equipment/processing intensive speciality products for tiny runs will be MINDBLOWINGLY expensive.

This isn't about the little tubes that go in a guitar amp... we're talking about tubes that may well be too large for a single person to lift.

What's more, everyone who knew how to build things is either dead or in a retirement home. You'd have to re-engineer much of it from scratch.