We don't have them readily in stock, Alan, but we could likely get one for you, it will depend on whether our supplier has stock and when our next order with them comes around. It looks like the price is around $100 - $150. 

G'day Jack,

The screw cap sizes on Platypus gear are the same across their range, so there's no reason why you couldn't attach a bladder hose to the clean reservoir.
Great idea!

G'day David,

As far as we know there are no other accessories available for their Gravity Works filter kits, however, the cap size is the same across their range of bladders and bottles, so you could grab one of their bottles with a push/pull closure cap on it and replace it with one of those if you wanted to reduce the flow a little when pouring into another container.

G'day Anton,

The Filter Life on the GravityWorks 4.0L is 1500L, generally, filters will have a number of Litres for their lifetime. For example, the MSR filters range from 1000 - 10, 000L. 

G'day Adriana,

Unfortunately, there isn't a specific way to attach this directly to a Camelbak crux, we have tried this out before and the tube sizes are different.

G'day Mark, 

We've just tested this in store and found that we couldn't fit the GravityWorks onto the Camelbak Military Bladder. The tube is a different size it also won't fit the Camelbak adaptor, so I'm sorry to say that you wouldn't be able to connect the dirty bag directly to your Camelbak bladder.