Alot of folks are running cases like these:   
http://amzn.to/mzWGQR
They can be picked up for about $35 and are perfect for open air mining.  It will be hard to beat that price point.

That same company offers a stackable open air case that I absolutely love. It runs about $50 bucks and I can stack as many rigs as I need on top of each other.  Check it out here:
http://amzn.to/jPdb7e