I can strongly recommend this model, the de luxe sidarn, when you've had enough walking just sidarn for a while
http://www.bin-to.co.uk/product_info.php?product_id=132
Seriously though I find mine ideal for days out with a fair bit of walking or standing, like an air show or folk festival, plus I can carry camera, lenses, and snacks in the box under the seat or hanging on the handles. Sat down the handles act as arm rests and ideal for steadying the camera like this last year at Swanage folk festival, camera on monopod in case I want to stand up. Excuse the hat, but I burn easy, the pretty pink bag is not mine I hasten to add, belongs to friends daughter.