Looking for a rear axle left castle nut. This is the one that is fitted on the sprocket side, with part number 75010181A. Has to be with the 'old style' finish, namely galvanised/zinc anodised (gold) and not the modern plain stainless steel finish (steel). See picture below. If anyone has, or has seen one advertised anywhere, for sale in near new condition, please let me now.
Strangely enough, they have a substantial variance in size on all examples of the 748/916/996/998 range, as can be seen from the picture below (obtained just now online).
Ducati 748 916 996 998 Rear Wheel Nuts Ducati L/H Rear Sprocket Axle Nut, Spindle, 748, 916, 996, 998, X4 Available
Thanks Paul @916ducati0 ; I've proceeded with the purchase earlier this morning from one of the links posted above by Roadtrip.