Skiing

This probably isn't helpful but might be worth a shot.

When I ruptured my ACL in Switzerland the medical centre in Zermatt gave me a Gibaud brand knee support. It's one with straps on the front and back and has a cutout for your patella. Metal braces on the sides too.

When I got back to the UK, my knee surgeon said that Gibaud brand are his favourite to recommend.

Can't find many for sale in the UK though....sorry. have you got a trip coming up? You'd be very welcome to have mine...I don't need it any more.

How good is your physio?
Have you seen a musculoskeletal specialist?
Have you strengthened it?

If you brace your knee and have a bad crash, you could just fuck your hip as the force will transfer to another part of the leg.

Take up snowboarding and save the knees for cycling. Skiing trashes knees and braces will only help up to a point.

I snapped my ACL over in Canada and was given a brace very similar to the one that @Stonehedge linked to - effectively hinged metal rods on either side of the knee joined by a neoprene sleeve. Was told by the consultant that her partner always wore his whilst ice skating etc.
Wore the brace for the first few trips for added stability / safety but I don't know how much good it would do in a proper smash - it did seem to help support the knee, so helped conserved knee stability/strength a bit longer, which i guess is the point, I don't think a simple neoprene sleeve would have had the same effect but YMMV. Even with the robocop brace, it certainly did not stop me still being very conservative about what the knee could do - it won't replace proper strength / stabilisation prep (which i'm sure you've been doing).