Never seen one with a built in check valve, I'd just add one inline to your O2 tubing. Morebeer has threaded stones.
Originally Posted by Revvy
And I'd like to see my 1.080 beers ready from grain to glass in a week, and served to me by red-headed twin penthouse pets wearing garter belts and fishnet stockings, with Irish accents, calling me "master luv gun," but we can't always get what we want can we? :)
That is just the first one I found, I've never done business with them and the page lists that same part in two different places for different prices so clearly they are not that organized. Your LHBS could probably order you one from Foxx equipment.