From the lovely and interesting store H.M.S. Beagle, I purchased a gas mask bag. They have a sordid history of being used to hold gas masks in WWII, but they are very sturdy and useful. I recently used mine on a trip to the art gallery. I HATE having to wrestle with a purse when I am going anywhere where I will be standing and looking, so I try to have a sling of some sort. This fits the bill well and I think is pretty stylish with jeans and a t-shirt. I hope someday to customize mine with buttons or embroidery or something – but I am using it as is for now.
As an aside, the store now has a really complete online store, and the gas mask bags are listed here: http://www.hms-beagle.com/xampp/htdocs/shop/index.php?main_page=product_info&cPath=142&products_id=7506