I wouldn't go any smaller then this for your RZ, 2-3 lens kit.
Spend some time looking through the bags and cases at sites like B&H.
Lay-out all of your RZ equipment on a table, simulating the pigeon-hole dividers, (like the link).
Measure the total width, height, and depth of the gear you want to carry.
Look for bags that have those [internal] dimensions.