You could try microsoft myphone. It'll back up contacts to a live account and restore them. You can set the program to sync manually, and just run it on your phone after work to get them back on. You wouldn't need a computer to restore them, but would have to manually select all contacts and delete them before work. They'd be stored on a server somewhere, so you may not want that if you only want them on a usb stick.
http://myphone.microsoft.com/