Check out the Sportube overhead backpack I posted above. It’s sized to meet airline requirements hence the name “overhead”I have never found a carryon that fits the size requirements and holds my boots. I use a wide strap (short shoulder strap) that clips them together and a small backpack for the other stuff I can't rent if luggage is lost. I can attach boots to pack during layovers but I carry my boots separately on the plane.
It does include a bungee hammock for your helmet so you cbs carry everything physically. Usually have to remove the helmet when I toss it in the overhead bin but can typically find a spot in the bin for the helmet.
and to be clear I live in Florida so I HAVE to fly to ski. So my pack gets a lot of use.