Up for sale here is this used vintage on/off power switch, dated 1965 and made by CTS. This is a nice little power switch. It has a 1/4" D shaft. This is marked 3A 125V, so it should be fine for most tube amps. It is guaranteed to work for you. Please see my pictures for details and measurements.

US shipping and handling is $5, and international is $18, no matter what quantity you buy. All my small parts are set up for combined shipping, so just use the "add to cart" feature and then check out all at once, and it will combine shipping. If you have any questions, please ask.

I have more vintage power switches and other vintage electronics listed--feel free to take a look!