I've seen them starting at $3. check out froogle and search.

An old name for Google Product Search. It let you compare prices of an item you wanted.

Use Googles Froogle search, check on eBay and amazon

I found a battery operated toe warmer online for $17.19 that may be of interest to you. The toe warmer can be found at the following address: http://www.discountofficeitems.com/cleaning-breakroom/climate-control/fans-heaters/heaters/cozy-products-cozy-feet-foot-warmer/p69981.html?ref=froogle&source=froogle&utm_medium=shopping_engine&utm_source=froogle. Another place you may want to check out is ebay.com because they have a lot of variety on things such as this.

CNet offers a great comparison tool. Google Froogle also offers the ability to compare prices.