While carrying it around in my pocket, my MiFi 2200 was always accidentally turning on and the battery running down. This is my solution, an old rigid plastic ID or credit card, taped inside a chewing gum package. The MiFi slides snugly inside the package and along with the rigid card, forms a protective sleeve around the MiFi, preventing the 'on' button from accidentally pressing.
I found a case at the Dollar Tree (for $1) that fits the MiFi quite well. It is a cheap rip-off of the http://alumawallet.com
. The Aluma Wallet does not quite fit, but the "Cleaver Wallet" does. Maybe just half an inch longer than necessary. I pulled out the accordion card sleeve and the MiFi 2200 fits right in.