I have been looking for exactly that boat for a few months now. They do exist but very few used ones around.
I did find a new one at the end of last year that the nameless dealer in a Manchester church was selling, but after half a day opening boxes in a warehouse they concluded they didnt actually have the boat
The only used option that I have found is either the Avon 340 or the Plastimo 350. After looking at both I felt they were a little too flat in the hull department and would not be much of an improvement over the Bombard.
There are also a couple of new options, my favourite is the Highfield 380, its around 70kg and takes a short shaft 25hp. They do a slightly lighter 360 as well.
CL 380 - Highfield UK
But if weight is really important they do an ultralight 340 at less than 50kg, but it only takes a 15hp
UL 340 - Highfield UK
Excel also do a nice 360,but its a real heavy weight at over 100kg.
RIBs Excel Voyager SR360 RIB. Excel Rigid Inflatable Boats. Quality Inflatable Boats Online
Of the folding transom ribs, the only one I would consider would be the Walker Bay 340. I have owned the Zodiac/Bombard/Avon 310 folding rib but it had a virtually flat hull (to fit neatly into the bag) and slamed in even small chop-clever tender though.
There is a couple of deep V options in this size range, but without exception they are all much heavier and take a long shaft outboard.