Honda CBR600 carburetor diaphragm 16111-MBW-601 
68mm OD  This is the only part avalible, Honda does not make this part anymore.
Price is for one.
NOTE you must install the loop seperate. 
1999 CBR600F4 A 
1999 CBR600F4 AC 
2000 CBR600F4 A 
2000 CBR600F4 AC