This was a while back but Brian Graham of Graham Tools/Pantera sold the newer version of the switch. My friend bought one and said it was a lot better quality and worked great. The new style replacement backup switch part # 06033aa. I don't know if the part number is Graham's or an actual manufacturer part number though.
The tool business is still on line but I don't know if he's still in the Pantera parts business but it wouldn't hurt to call. Here's a note I found on the website "A blast from the past...Graham Tool Company sold parts and provided restoration and customization services for DeTomaso Pantera owners. Our first company logo was designed by Chip Foose. It was in a shape that represented two new business ventures...teeth and tools. But what happened to the Pantera parts collection? Stay tuned...in fact.. we still have lots of Pantera parts in storage. What are you looking for? Call toll free at (888) 262-2550 or email Brian@GrahamTool.com"
Here'a the new switch installed in my friend's car -
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