Camera Bags remain a really popular choice.  This is a narrower, taller style perfect for days out. With a single zip at the top, there's also a zip on the side for easy access. They come with a detachable, long ,adjustable self-coloured strap but you can dress it up or down with additional funky straps.
 
Silver colour hardware
Internal pocket
 
Dimensions: 15.5 cm (L) x 6 cm (W) x 20 cm (H). Drop (of long strap): 61.5 cm