Ruggedized Meters [ http://www.hoytmeter.com/ ]
At Hoyt Electrical Instrument Works, all meters (both analog and digital), testers, transducers and various panel-mounted components are built to satisfy the most demanding customers and are built to last in the field.

Vacuum Tubes, Inc. [ http://www.vacuumtubesinc.com/ ]
Offers new and used industrial and electron tubes, radio tubes, audio and guitar tubes, tube testers and sockets, and capacitors. Includes online ordering and catalog, and literature lists.