I was at a local marina earlier picking up a prop. While waiting I started looking at the fittings they had, everything was brass or stainless. I noticed the bulkhead fitting in the link below. It was $10 so I grabbed it to try on my round igloo cooler. It fit very well and was totally water tight. All I need is a valve for it and my MLT is complete.
I'm wondering about using one on my keggle, I think all I would need to make it work is high temp orings.