Dunlop still have the K177 (120/90-18) and K555 (170/80-15) on their website...
They are (one or both) O.E. on Honda Magna and VTX 1300/1800, Shadow and ACE, PC800, Kawasaki ZL600, Suzuki Intruder and Yamaha V-Star 1100 Custom (according to a web search). Try a Honda dealer?
