How about those "Tire Balls" ? I know they are available for ATV"s and such, not sure if they have anything available for a tire such for a sulky.
I searched the site and didn't find anything but then on the "Agriculture" picture it showed "Worry Free Lawn Care" so they may have some stuff but it just isn't on the site. Who knows...
2003 Silverado 1500HD
7x16 enclosed trailer
Walker GHS 36"
Encore Premier 36" WB