The Valvolo.com online store carries USB warming kneepads. Here’s the copy from the catalog page:
You can have a pair of USB heating gloves when you feel your hands freeze. You can have a pair of USB heating shoes when you feel your feet freeze. However, you will wonder how about the icy knees? Don’t worry! A pair of USB heating knees can help to keep your feet toasty while you are working near the computer under a chilled environment or in winter time.
As of this writing, they’re going for US$19.99 with $6.00 shipping and handling. Pair it with a Successories inspirational poster and you’ve got the perfect gift for the office suck-up!