I a couple of years ago looked around locally and didnt find one like the one in your photo ... doesnt mean they are not out there though!
Fraser RV's online parts catalogue
has one similar to the one in your photo. But it appears its a wall mount type.
I was thinking about making one similar to the one Joy A made (yet another great Joy mod) There is old post Mounting a single Propane tank
which Donna posted some photos of the actual mod.