Try a place called NRP, telephone number (uk) 01618328646. past them the information and the will sort you out.

This company extremely good, with motorbike Carburettor Diaphragms.

It`s best to change the both carbs and the fuel cut offs diaphragms at the same time. Changed them on my bike about 80,000 miles, now touching about 100,000 miles and still going strong. RDO4 1991
If anyone uses them then please post back with an experience.