A few years ago in Colorado I took a bad spill beginning of the season and really hurt my knee. I had it evaluated by a Doc (badly strained MCL) who prescribed a brace. It was a monster - not like the little spandex things you can buy in a drug store - went from high calf to almost mid thigh, lots of velcro and strong lateral support. I think it may have had some metal in the sides - can't recall. Anyway, all that said I hardly noticed it being on when skiing, so I wore it pretty much the whole season, long after my knee got back to feeling normal.
Mine was a little different but something like this...
If you go to a Sports Med Clinic/Orthopaedist in a ski town they will likely have a room (if not a warehouse) filled with these braces and also moonboots and other wearable stuff used to deal with common snow injuries. And even though the price is of course ludicrously high, (like everything else with healthcare these days), if you have insurance you may be covered for most if not all of the cost.
Good luck. ;-)