FYI - I'm just back from a gas bottle replacement trip to Hop & Grain in Marrickville. I noticed they had clear water filter housings (with a blue top - look very similar & size to the ones in Kris' photo a couple of posts back). Seems like a pretty solid unit - brass screw threads etc - was told they sell for $30.
Hmm, this looks like it: http://www.thehopandgrain.com.au/pro...filter-system/
I know nothing more of the unit, but this thread immediately came to mind.