Hi Buddy
Have you considered making one ?. I was looking @ one last week(had it bookmarked on another PC that i only use infrequently) and it uses a water filter housing identical to one that i have just bought off Amazon for GBP15.
Bowl is filled with coolant, regulator controls inlet pressure to the bowl. outlet is 3/4 BSP Female, has an adaptor with two small bore tubes brazed in it. one just takes air from the housing the other has a small tube going to the bottom of the filter bowl to pick up the coolant. two tubes from the adaptor go to a mixing head were you can control quantity of air & coolant.
Mike