Look for a switch

[Htmlkid]

Can anyone help me find this switch.

 

[LANCECASPER]

I found it . .it’s right there in the first picture . .  lol

 

If you’re looking for a new one you might have to pull that and see what it’s rated at and who made it. It looks like it’s been replaced. 

Once you find that information then something like this might work: https://www.aircraftspruce.com/catalog/elpages/racbezelswitches.php?clickkey=4681 or https://www.steinair.com/product/locking-toggle-switch-spst-onoff/

However if your avionics are staying on with the master off it's likely your relay.

[PT20J]

It's called a locking lever toggle switch. They are commonly made by any number of switch manufacturers. But, you need to know the current rating and the configuration. It's probably a SPST controlling a relay, but you should check it to be sure.

[jetdriven]

locking bat toggle. Mouser has them.