I usually make my own, by using the appropirate size female part, and a male part that goes from the correct size thread to a +1 size slip fitting, and mash a rubber gasket between that and the glass.
Example: I'm working on a small fuge right now, I'll use 3/4" drain PVC, I have a 1" hole to fit threads from the male piece from the inside of the tank into 3/4" PVC T fitting, then run a durso stand pipe and drain side of course off the T. The male end that comes from the inside of the tank has a 3/4" fitting on the thread side, and is a converter piece from 3/4" thread to 1" slip. That way the 1" part provides a flange for greater area to mash the rubber gasket into the glass.
They're just as reliable and way cheaper. It can be helpful to lubricate the gasket first to ensure you get a good seal the first time, but don't over tighten either.