I use the Camco Gen-Turi.. advantages are it is easy to assemble and attach, take off and bag, it has only once gotten too hot to touch, (That was from the heat of the sun, NOT the generator) I've run with it for 24 hours straight and still able to hold on to the black pipe for over a minute comfortably (just do not touch metal parts) And it is very light weight.
I have seen home made versions.. Some get hotter, and all of 'em are heavier.
Do not park next to me without one if your generator exhausts towards me please. (either home made or store bought, I don't care.. Just make sure you have one)