I haven't found sources for a new switch, yet, however
For a YARD SEARCH on-line, I use; https://www.hollanderparts.com
A yard that uses Hollander Interchange can search other yards and have it shipped. If a specific part, such as the switch isn't listed, search again for the next higher assembly, such as in this instance, the transfer case.
I searched and found, 1987 >Ford > Bronco > Transmission > Transfer Case Assembly > 00206A Electric Shift, Id E9ta Ma