Hi, I've been thinking about adding a diffuser to my S3 to tidy up the rear a bit as the gaping hole looks a bit unfinished although I've lived with it for over 7 years!!

Does anyone know where you can get diffusers from, roughly how much and just a little detail on why they need fettling when it just looks like it needs to be screwed to something...??

If there are multiple answers / sources I'm in Surrey, so somewhere in the South East is preferred.

Many thanks!