I literally just bought a 14' one of these off Etsy in October for more but if you're ever looking for a cheaper, shorter alternative, ThinkGeek just added this 12' one to their website:
http://www.thinkgeek.com/product/f0dd/ I know most handmade ones cost more so it seems like a pretty good deal to me! Not sure on the quality or authenticity of the colors yet but they seem nice in the photos.
Oh and if for some reason you have never looked at ThinkGeek, their Doctor Who inventory on their site had grown HUGE over the last year:
http://www.thinkgeek.com/brain/whereisit.cgi?t=+doctor+who While I am speaking about Doctor Who merchandise on websites, I may as well mention this awesome site as well:
http://www.bigbadtoystore.com/bbts/search.aspx?search=doctor%20who