What do you guys use for chassis wiring on old tube gear?

In the old days, when I needed to replace some bad wires in an old tube
radio, I just salvaged some from old tube tv sets. But dont have them
anymore. Looking on places like ebay, I see suitable sized wire, but
most is rated at 300v or usually less. MUCH LESS.

My local hardware stores have "Automotive wire" which is generally
thicker than I need, but also rated at lower voltages than what is in a
lot of tube gear.

Personally, I cant see that thick insulation failing at 500v or so, but
it is a concern.