To make something more sensible from BringMeMyFix's comment, you could go with a 100mm front disc hub and put a couple of 5mm spacers on the axle, then drill and bolt your fixed sprocket (you will need a bigish rear cog) to the 6 brake disc mounting threaded holes.
To make something more sensible from BringMeMyFix's comment, you could go with a 100mm front disc hub and put a couple of 5mm spacers on the axle, then drill and bolt your fixed sprocket (you will need a bigish rear cog) to the 6 brake disc mounting threaded holes.