Hi Kristen,
Welcome to the site!
They're quite a commodity and pretty hard to find. Usually you'll get them through liquidated stocks along with other designer handbags. Here are a few suppliers you can try to check out:
Link hidden: Login to viewLink hidden: Login to viewLink hidden: Login to viewLink hidden: Login to viewLink hidden: Login to viewAlso, if ever you are interested in pursuing this further you can contact Guess directly, here's their address:
GUESS, Inc.
Licensing Department
1444 South Alameda Street
Los Angeles, CA 90021
U.S.A.
Hope this helps. Cheers :)