I've been doing some digging around for a cheap but functional case with room for accessories as I'm making plans to blow my tax refund on a C3000 in a couple of months.
I grabbed one of
these (the PTA-801) at Microcenter for < $3 a couple of weeks ago. Can't seem to find it at the Microcenter site, though.
Anyway, it holds my 5500 in a cheap slip case, USB thumb drive, 2' USB cable, 7-way card reader, peakcloudy battery pack, plus CF wireless card and modem with room to spare. Might work for a 3000.
It's nice, heavy nylon, with a decent amount of padding, and seems to protect everything well enough bouncing around in my satchel. Plus, it looks more like a toiletry case than something that holds an expensive gadget, so maybe it'll deter theives.
Unfortunately, Microcenter doesn't seem to have it online. I found it in with the camera cases.