David,
I was never able to find a perfect case for my monorail camera, a 5x7 Sinar P2. For casual transport, you might want to consider a "wide mouth" duffel bag from LL Bean, available in several sizes. I use one to because it is high (deep) enough to leave the camera fully assembled - attached to the 12" rail. It also has room for my 3 lenses, filters, meter, etc. I carry a separate Zone VI film holder bag. I've carried this on the shoulder strap for up to 2 miles from the car, though my wife carried my film holders in this instance.

N.B. If your wife carries your film holders for 2 miles to the most scenic waterfall in all of Michagan, you had better at least pretend to take a picture, or there will be repercussions!

Take care,
Tom