Here is a link to a company selling a battery for $25 for the 505...also includes a 9:40 video (scroll down the page a little) showing you step-by-step how to replace the battery:
http://www.newpower99.com/ProductDet...5&Show=ExtInfo
Video alone in on youtube:
http://www.youtube.com/watch?v=iLHgLz9LYMA