I ordered a clip on from eBay for $6.95. It has a single LED and takes three AAA batteries. It has rubber on one side of the clip and I put sticky back foam weather stripping on the other side. It has a flexible goose neck and works pretty well. My only complaint is it is a bit bulky and throws off the balance of the device.
Here is a link
http://cgi.ebay.ca/Led-Book-Light-fo...item414fe40d4f