I had the same issue of finding a hitch plate when I was upgrading to the K66 on my X300. Finally I bought a new one from Green Parts Store for around $180.00 plus shipping. Second hand X500 hitch plates are hard to find and even if you find one the asking price is usually north of $100.00. Since my X300 only had 68 hours and since I plan to keep it for a long time, I decided to buy new.Husqvarna star shaped hub. 586935402. Funky looking, but cheap. 1” hub. Almost too easy. Next hurdle is finding a second hand X500 hitch plate. Versus modifying.