I recently purchased the Cateye Micro wireless off an Ebay store for a whopping $35 including shipping. It's very basic, but functions perfectly. I've only got about 200 miles on it so far, but if you're looking for something small, basic, and simple with no clutter, I'd highly recommend it.

http://www.cateye.com/en/products/vi...d=6&subCatId=0