I recommend making your own, as you can get a much larger surface that way. Also, it's much less expensive and more portable (lightweight). Here is a link to some Youtube videos that show you how to do it:
http://www.youtube.com/watch?v=g14govA4pIM
http://www.youtube.com/watch?v=yAS25v3ZTk0
http://www.youtube.com/watch?v=A0lk7UBQgZY
Here is a link to her list of videos on the topic. There is a fourth one (update) that adds to the previous three. She also has one on ergonomics of sewing:
http://www.youtube.com/playlist?list=PLBF5C338341F28BF9
Edit: If you do a Youtube search on "quilting table" or "sewing table", you will find other ideas as well.