I think I've finally found it. On Ebay I scored these Sorel brand Medina rainboots. They have actual tread on the soles, they're totally waterproof, and while I wouldn't say they're as thermally armored as some full-on Joan of Arctic snowboots, they do stand up to the cold better than a pair of Hunters, which are almost counter productive in their inability to withstand any kind of low temperature whatsoever. I popped a pair of thermal inserts into these ones and they're toasty warm now.
This seemed worth mentioning at this brutally cold winter apex. Keep warm out there.