Years ago I used a Kirtland Tour Pak handlebar bag for everything from a six pack of beer to my SLR, three lenses and flash to a full kit of safety testing equipment on the job. I added my own padding/inserts as needed. Unfortunately I gave that bag and rack away several years ago. Wish I'd kept it, now that I'm riding again.

Check out Velouria's Lovely Bicycle blog. She's also a photographer and totes her largish Canon dSLR and lenses in various bags, panniers and handlebar bags.

I no longer tote a full sized dSLR so my Lowepro Off Trail works fine with my compact cameras. I just wrap the waist belt around the handlebar and stem as a makeshift handlebar bag.