Maybe I missed the scope but, why are you so worried?
If you have a low current circuit, a 7805 is just fine for up to 35 or so voiltages.
If you have higher currents, then a smps like the expensive Recom that Richard uses or the cheaper https://gr.mouser.com/ProductDetail/490-VXO7805-1000 I use is good enough.
And last but not least, the circuit that you posted for reverse polarity protection with the p-mosfet in post #14 is the best protection with no voltage drop.
Ioannis
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