Don't know the Tranjo, but I've owned and played a Sloan Traveljo for about 30 years, from back in the days when Sloan called it a Fold-a-Jo. Handy for air travel since it fits neatly into a brief case or similar carry-on. Beware: the pot and all those strings look really weird in security's x-ray machines, and the guys working the scanners tend to freak out when they see it.

My version takes nylon strings, which gives a mellow sound but not necessarily one that is loud enough for performance with other instruments.