It's been a year or so since the last time I did this, but I have had success carrying on poster tubes of that size. Most often I find that it will fit in the back of the overhead bin if you can find one that does not have any bags in it yet (though this may affect wheels-in stowage of others' bags).

Depending on the aircraft, I have also occasionally been allowed to stand it upright in the closet up front. I use a look of extreme supplication and mild desperation when I ask/beg the FA if I may please stow it in the closet. (Just don't forget it when deplaning!)