Fork top plug 36 mm wrench
Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models
Thanks to Hayden for sending me this information via email. In Hayden's own words and photos:
Just got a very small, 36 mm Oil Filter Socket. Very cheap at £4.50, Perfect for fork top nuts, and fits with travel tool kit on bike. Advertised on auction site for Mini, Vauxhall, Ford, VW, BMW, GM, Mercedes, Volvo & Golf. May be of use to others
I may weld a short bar onto it so I don't need a 1⁄2 inch drive.