Guy,
It would be easier to build one from scratch, or from various parts. (Imho)
All the parts can found at your local hardware store that carries BBQs.
(Burrner, regulator, ignitors, replacement grills, etc.)
A pot with a lid, or a turkey roasting tray with lid of the right size would do the trick for the cooking chamber.
The biggest issue that I see, is getting the burner far enough below the grill and still keep the overall unit size small enough.
I'm probably going to end up designing and building my own BBQ for the tear, like my little Brinkmann Smokin' Grill except smaller and I'm looking at building my own mini range like the Flamineta.