I have used the Klim covert socks to achieve waterproofing with a motocross boot in both a sidi crossfire and tcx oxtar boot. I do not need waterproofing all the time but on a ride where there is potential for a soak or cold wind I will wear them. Keep in mind that these socks are a two layer system and will feel tight in your boot. To compensate for this , I remove the insole of the boot. I have had good luck with this system for the riding I do.
I'm so far behind I think I'm in first