I have an ortlieb compact handlebar bag that I really like.
http://www.ortliebusa.com/cartgenie/...p?pid=90&cid=2
The strap snaps on and off very quickly, which is handy if you are impatient like myself. The handlebar mount is quick release. I stored all those things you mentioned, although I had a small fixed lense on my camera. An SLR may not fit with a zoom lense, I'm not sure. It is totally waterproof. I rode two days in the pouring rain in Japan and all my stuff stayed dry. I put everything in plastic bags too as a precaution, but no water got in. You may want to look at one of the bigger ones too. I like my handlebar bags small, but it may not fit all your camera stuff.