1943mike:
Out of curiosity, if a pre-built case is too much, do you have access to basic hand tools?
Also, do you mind if the "case" just protects the model from dust but is just basic protection?
Hardware stores sell screen door repair components that can be used to construct a temporary enclosure by substituting clear shrink fit plastic sheeting of this kind
http://tami-port.suite101.com/plastic-window-insulation-a35412
for the normal insect screen.
You would need to have a sturdy base that can hold stiff , vertical columns that the aluminum panels can be attached to.
For instance - 4 pine 2x2 vertical poles would suffice as supports that the screen hardware can be attached to. The 2x2 lumber would need to be attached to a strong base to hold the panels securely and prevent damaging the model.
If you know someone with a router or table saw, cutting slots deep enough to slide the panels into the 2x2 is possible- or just attach the panels to the exterior of the 2x2 pine vertical supports.
The top panel can be made the same way as the side panels.
Not as nice as a professional case, but it will keep dust off and the window film is very clear, allowing a view of the build.
Let me know if my suggestion needs further clarification.