I thought I had already responded to this, but guess my message (or me) got lost in cyber space.
I have a cane that folds down into a tripod based seat. I can't travel without it. Cost under $30. I got mine at Magellan's and have had so many people ask about it that I really should be getting a commission by now. You do have to straddle it to sit or it isn't stable, but it significantly expands my options, as I have to sit down frequently.