I've just bought this bag off eBay for my OM-D. The camera is small, so a lens fitted to the body, another lens plus a battery or two is all I want to take on my walks. Travel light! Billingham bags are brilliant, but they are several (many) hundreds of dollars these days since becoming popular. This looks fantastic for around $50 posted (Aust):
http://cgi.ebay.com.au/ws/eBayISAPI....ht_8486wt_1180
The best part - $55 landed in 10 days
This one is designed for a full-sized DSLR and a lens. They have larger ones too. I'm very happy with the satchel style of bag these days. Bags with a dozen compartments and all the tricks are great, but these are so practical once you've used one. Much better for a quick grab and go.