Finally got rid of my dirty tail light, I tried to clean it by removing the cover, but broke it instead, so replaced with a salvaged part:

Original light:
http://www.flickr.com/photos/67048934@N06/7042650911/http://www.flickr.com/photos/67048934@N06/7042650911/ by http://www.flickr.com/people/67048934@N06/, on Flickr

Cracked when removing the cover to clean:
http://www.flickr.com/photos/67048934@N06/7042660045/http://www.flickr.com/photos/67048934@N06/7042660045/ by http://www.flickr.com/people/67048934@N06/, on Flickr

Fitted replacement part:
http://www.flickr.com/photos/67048934@N06/7042658659/http://www.flickr.com/photos/67048934@N06/7042658659/ by http://www.flickr.com/people/67048934@N06/, on Flickr

http://www.flickr.com/photos/67048934@N06/7042661675/http://www.flickr.com/photos/67048934@N06/7042661675/ by http://www.flickr.com/people/67048934@N06/, on Flickr

http://www.flickr.com/photos/67048934@N06/6896568526/http://www.flickr.com/photos/67048934@N06/6896568526/ by http://www.flickr.com/people/67048934@N06/, on Flickr