I just made a bong adapter for my pax. I had an old aluminum slide for my bong and found a rubber end cap around the house, cut a hole in the end cap, and pulled the aluminum slide through it. My end cap is really similar to those battery end caps for the launch boxes so any mflb owners want to see if it fits over the mouth piece tightly, you guys have a good piece to use as an adapter for the oval pax mouth piece to a round slide.
Edit, here are the pics. It was a bit of a squeeze, but it makes for a tight seal.
Slides right over the mouth piece.
And a perfect fit in the bong!
It's just a cheap $20 bong from a local head shop, but it gets the job done!