Often the switches used in equipment are customised to some extent and exact replacements are difficult to obtain.
If you can find a switch that has the same (or greater) voltage and current ratings and you can fit it in, then thay may be your best option.
If the cosmetic appearance is not critical you can drill a new hole and mount a new switch. I had a amplifier for years that had it's faulty push button power switch requred to an silver toggle switch mounted next to it.
If you want a close replacement, we'll need photographs (unless someone here has direct experience with this model amplifier)