But make sure it's automotive grade. Same thing happened to me when I bought mine used (two weeks ago). I went to HD and they did not even have anything close, and what they did have was cheap chinese tin anyway. I went to the U-haul place (it was a U-haul hitch, not a HH) and I said, "I just bought a used hitch from Craigs List and there is no center u bolt. Can you sell me one?" His reply was - "You just bought a hitch from us and there was no u-bolt? They must have missed it when they were assembling the hardware package. Let me get one for you." He checked his inventory and they had one in stock. He went and got the hardware package, tore it open and took out the bolt and two nuts, handed them to me, and told me to have a nice day. I think I like U-Haul.
(almost a 2 E family on Father's day - but the "closer" was a jerk and we walked).