It will likely be a Guzzi part also. Find the part number from the parts book (on Benelli Bauer online if you don't have one) and search on the internet. Motomecca, Gutsibits and Stien Dinse and TLM have most parts. I suspect it's the inlet rubber off a guzzi small block like the v35. If you let me know the inner dia I can compare with what I have here.
I get part number 61114300
Which is the inlet rubber for the small engine Guzzi with the square slide carb. V50ii, V35i etc