I am a big backpack person, even though us backpack carriers are frequently mocked. . . mainly because I spend a lot of time in the back bowls at Vail and huge, spread out Snowmass, and I can't easily run back to the car or the village for things like heaters or sunscreen or my camera or whatnot. When I was still skiing the east coast and it was easier to get back down to a locker or my car, then I didn't carry one, but now I find that I often need more than what fits in pockets, so I have given in. On warm, sunny days, no pack. On ominous days, pack. But small, and unobtrusive. I, too, laugh at the inbounds skiers carrying what look like 3-5-days of backpacking supplies.
I use a Black Diamond Bullet pack, which is a conventional pack, but very small, even though it does have a sternum strap and hip belt to keep it in place. I usually don't have too, too much in it, but it has been just barely big enough to hold my secret weapon on Arctic days. (Super lightweight, rubber soled bedroom slippers and a change of socks that I slip into in the on-hill lodge, so I can warm up boots and feet.)
Arcteryx used to make a pack like you're describing-- a bandolier, but it had hip and sternum straps to keep it steady when you were skiing, but I am not sure they make it anymore. Patagonia's Atom pack might work, but I've never carried it, so I don't know how stable it is. HTH.
