I use a fairly small, reasonably light camera bag that was sold as a part of a kit with a consumer grade Canon digital SLR camera a few years ago. It has just enough room for my C330 with waist level finder, 65mm and 135 lenses, a few rolls of film, a hand meter and a couple of smaller accessories.

EDIT: It looks similar to this one: http://www.expansys.com/canon-camera...100-eg-169690/

I have bigger bags when I want to take along the trigger grip, the prism finder and a paramender.

Further EDIT: I see that one is actually heavier than what the OP is using now - oops.