18-inch Trials-Universal tires from the late 60s are still around. That was the tread on the rear of the mild bobber '69 XLH Sportster used in the TV series 'Then Came Bronson'. Goodyear, Carlisle, Dunlop, Barum, IRC, Perelli and others. I have one on my '67 Triumph T100C. I find most of them at swap meets. Ask you local dealer if they do business with DIXIE International from Ohio. I get that tire tread in a 19-inch IRC brand and they are still wrapped and good.