Well, I finally got my accessory disconnect switch installed! I used the same switch that RetiredBob used. I couldn't figure out how to make the light in the switch work.
In order to make it snap in easily, I used a flat file and filed down the top and bottom of the plastic retainer opening (not the front opening). It didn't take much, you could get it TOO large.
I found this mini "add-a-circuit" to use as an adapter to plug into the fuse panel to attach the leads going up to the switch. I didn't use it as an "add-a-circuit" with the extra lead, but just used the connections on top where the original fuse is supposed to plug in.
Littelfuse Blister Pack FHM200BP - Fuse Holder | O'Reilly Auto Parts
I used these spade connectors to plug into the adapter above for the wires going to the in-line fuse and switch. I put the connectors in a vice and filed them down to about 1/2 the normal width so they would plug into the mini-fuse adapter.
Dorman Conduct-Tite! 85453 - Spade Terminals | O'Reilly Auto Parts
Finally, I used this mini-fuse in-line fuse holder between the fuse adapter and the switch, with the original 7.5A fuse in it.
Littelfuse Blister Pack FHM2BP - Fuse Holder | O'Reilly Auto Parts
Hope this makes some sense. I should have made pics but didn't do it!