The JR Products one looks like mine, except for the removable piece on the bottom (the screwy thing you mentioned).  I missed this one as I was searching with Prime-only enabled as I only had a few days before leaving on a trip with the Scamp. 

It appears the outlet to the grey tank has had a crack in it for quite some time and I finally noticed it was leaking this week and thought "how hard could it be?".  The factory folks squirted a healthy amount of silicone on the threads before assembling it and it was a major job to get the trap out of the sink. 

Don't know what kind of silicone they used but I've had an easier time removing parts with the threads epoxied together.  I ended-up removing the faucet, and the sink, so I could take it into the workshop and employ more drastic measures.  I managed to get the trap out without a scratch on the (plastic) corner sink much to my surprise.

Thanks for your help, I'll order up a replacement when I reach my destination.