Have you ever gotten tired standing in museums or on long walking tours? A few years ago I came across something called a "FlipStick". It is a combination cane and "leaning seat" based on an English shooting device. In one position, it can function as a very stable cane, and in the second position, you can push a button and rotate the seat to create a "leaning" stick. The collapsible version collapses into the size of a bicycle seat and comes with a storage pouch.
I don't really need the cane function, but my wife and I like to go to museums and read most of the comments, and there are rarely seats where you need them. Also, on walking tours where the guide gives an extended dialogue, it comes in handy to rest on. It even comes in handy waiting for trains or busses. I've used this on every vacation since I purchased it! Many times people have asked me what this device was, and when I explain it and let them try it out, most have said that they were interested in purchasing one for themselves!
Note that this is not a "seat" that you sit on. You form a tripod with the pole and your two legs and lean on the seat. It takes most of the weight off of your legs and is kind of like leaning against a rail.
You can purchase it on Amazon but the price really shot up since I purchased mine 5 years ago. You can go directly to flipstick.co.uk and purchase it for half the price compared to Amazon. (I have no affiliation with the company!)
Hope this helps and have safe travels everyone!