These boot backpacks fit in overhead compartments?
The Dakine boot pack mentioned above, yes, definitely.
On my trip to Jackson, I fit in boots, yak trax, all clothes needed to ski on day 1, googles, gloves, computer, iPad, chargers, book, and a few other things. I was able to cinch it down quite a bit even with all that in there. It was comfortably small enough to fit in the luggage size test thing, and had no issues fitting in the overhead storage.