I just rebuild the one I bought on CraigsList. The rebuild kit is new plastic washers and Nyloc nuts. You'll also want to buy new boots. I think the kit and boots costs $35. Take pictures of everything before disassembly.
You'll need 1-1/16 and 1-1/8 sockets and a foot long extension to get at the nut on the top of the main bolt holding the bar to the receiver insert. Remove the Nyloc nut down inside the receiver insert, back off the 2 bolts on the side and unscrew the main bolt from the collar inside the receiver insert. They didn't give me all the washers for this connection so I reused the old ones. Also, this was a 3/4-16 schedule 5 bolt that I replaced with a new schedule 8. It's the one bolt that if it fails will cut your dinghy loose.
I took the whole tow bar apart, sandblasted the rust off and gave it a fresh coat of black Rustoleum. Use white lith grease to coat the new washers and take the Nyloc nuts down enough to snug up but not bind the moving parts.
Here it is all ready to go back together with the new boots.
Jerry & Jeanne
1996 Safari Sahara 3530 - 'White Tiger'
CAT 3126/Allison 6 speed/Magnum Chassis
2014 Equinox AWD / Blue Ox