3-speed backup switch for a '68

I'm wondering what other backup switches will work for this application. I can't find a 3-speed backup switch for a '68, but I can get a backup switch for a 65-66 3-speed, and the 4-speed toploader.

When looking at diagrams, it looks like the same backup switch is used for the 4-speed and 3-speed transmissions. Is this true?

Thanks,
Jake