The carb on the Nova Rossi had a remote mixture sleeve/arm that worked
on a stupid left hand threaded course brass outside thread.If you lock it down to use the screwdriver slotted main needle and later forget it was left hand threaded when you want to undo it, it usually shears the brass thread.
The carb has a 16mm base which isn't common with most of the mainstream OS heli or Webra carbs.To use them you would need to make an alloy sleeve to increase the diameter to fit in the crankcase carb opening.
The OS60B i don't think fit's because it fowls the crankcase i think.It would also need it's special heat isolator sleeve removing and an adaptor making.
The 60L from the OS91 has a 15mm base so would need an adaptor
It has a 10mm venturi.I once tried an OS6H with the Nova Rossi,it had a 10mm bore and the power was insane.The 6H was for an OS61SFNH it had a too weak midrange though on the Nova Rossi
A super tigre 60 carb would do and has an 8.8mm venturi but would need an adaptor sleeve
.I've tried an ST60 carb before in the past on the NR60 and it was down on power.They do larger bore version though which was used on the later 60 heli engines,known as the "LC" carb
Just engines have various twin needle aero carbs available in 16mm base for under 20 quid .The carb needs to have a 16mm base with at least a 9mm venturi or the engine will lose power ,as Nova Rossi's are gas flow optimised and transfer ported to oblivion
Also try John White models,i seem to remember seeing various
carbs in the Vario catalogue for their WEbra and OS engine sets
,i bet they're not cheap either
Robbe/Schluter UK were the agents for Nova Rossi,maybe they have a carb left in among their old ****.I bet they'd still charge about 40 quid for it though;-)