Ah, I know that problem. A Hadley Pro insert is your answer... That plus a trip along your local high street to Gap, Next, even M&S and the like. My most used bigger bag is a Hadley insert - which will take what you have listed - inside a waxed cotton messenger bag which cost me about twenty quid from Next. I have added a Domke USPS shoulder pad and I can carry it all day. It's big enough for a load of other bits and bobs, and a light sweater, gloves, hat, scarf, etc. I'll pop off a photo tomorrow to show you what I mean. It looks like nothing...