Every Malossi rubber bit I have bought seems to made of some super-stiff rubber, and the bellows appear to be around 10% smaller than Piaggio ones.
I discovered that the Malossi bellows fit perfectly inside the MRP 'Dumbo' hose (or any 60mm flexi hose). I cut it back, to shorten it and to get rid of the angled bit on the end, and then 'screwed' it into the 60mm hose. Perfect fit, unlike when I tried with a stock Piaggio bellow. Fitted between carb and frame, it works a treat and so much better than with the Dumbo metal frame connector.
You can get the hose that they make the Dumbo out of from hydraulics/hose supplies places. I got some in black rubber which I think looks better, but you can also get it in clear as well. I got some 50mm and 65mm.