Oof, those dual pots with the end-of-track switch are really hard to find. I've seen them being sold by one reputable (but overpriced) eBay seller for over a hundred dollars each.
I think Blore Edwards has something in their catalog that would work (it's been awhile since I checked), but I don't know what MOQ would be.
Honestly, it's not the sexiest solution, but you might consider foregoing the switch on the pot and adding a simple toggle switch to the front panel. Obviously not quite the same to operate as an end user, but functionally identical.