I've something like that... Its a stone attached to an old racking cane with a valve... I guess it does work, but you have to swizzle it around for a while... You send me your address via secret email, and Ill send that to you.. Sneezles61
Seen them, never used one. You could go much cheaper by adding a stone/tubing to the gas in post. Of course I still think the CO2 will need to hydrate.
Other option, blow the CO2 in the liquid post... if you want... Sneezles61