I got mine from a local hydro shop about 4 years ago... I've had a look on-line and they dont seem to be about anymore... HOWEVER I found a LINK to a very similar one :-Where did you purchase that little carbon filter? I've been looking for one similar in size to that one.
http://www.gardenofedenhydroponics.co.uk/product.php?productid=480
Its the 1st one on the list in the LINK 100mm dia.X 150mm height
Hope thats of some help dude!? - ZTELTHY
...OOP! Thats just the cover...but I'am sure there's prob a Filter on this site too...I'll check in a bit for ya - ZTELTHY