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