I spotted this IIlBeCa Hudson Street cross body recently and really liked the way the shoulder-bag style has been married with the utility of a cross body bag. It doesn't look slouchy or too casual but perfect for wallet, sunglasses, a mobile and you are good to go.
Available in turquoise (below), viola or white, they're reasonably priced so if you want to be a bit more daring and use it to add a splash of colour to your wardrobe you can do it without feeling like you need to make a long term 'investment' decision!
NB. Enquire on the site for international shipping rates