I hate carrying poster tubes to conferences. They’re awkward and it’s an extra luggage item on the plane. Therefore I’ve started having my posters printed on fabric, so that I can just fold them into my suitcase or backpack without damaging them. The best quality I’ve achieved so far was with the fabric printing company “Spoonflower”; see this Astrobites post for details. However, they’re in the US and it takes at least 10 days to get the poster from them, so that’s often a no-go for me. The second best and completely okay option I’ve found is having the poster printed on canvas by a local print shop, like they do with photos if you want to hang them on the wall. For personal reference, I use “Canvas Express”, they print on A1 with some extra white space around (which looks fine even compared to A0 paper posters), link. The posters fold up fine and the lines are gone ca. 30 minutes after putting them up. Plus, they make a pretty good cat toy afterwards.