I always bring a bag. If I'm doing open to close then I'll do a locker rental so I don't have to carry everything all day. I like to be prepared so I carry: Fan, advil, electrolyte replacement tablets, cooling rag, water bottle, camera, extra battery for phone, gum or mints. My bag is usually pretty empty but I like having a bag big enough that I can put my headband ears in them for rides so that I only have to worry about grabbing my bag when I get on and off rides. I usually have a regular size backpack but trying to go to a small crossbody backpack - I bought this one. So far it's been comfy when I've done tester trips to the mall and museums. I like that I can swirl it to the front to open get things in and out without having to take it off.
https://kavu.com/collections/view-all-bags/products/paxton-pack?variant=12113503092807