[Pahaska]

A lug wrench that fits.

The one for your tow vehicle often does not fit the trailer. I like the 4-way wrenches that fit most everything and are easy to get leverage on a tough klug nut.

Duct tape.

When I went to Copper Canyon, Mexico, a few years ago, the tour operator required that every RV carry a roll of duct tape. We used to call it 100-knot tape when we used it on our gliders. You can nail down anything loose with it.

Tool kit

I carry one of the fitted toolkits with a variety of wrenches, sockets, and screwdrivers. Sears has this kind of kit, among other places. Mine aren't expensive tools; variety is more useful than quality. I also carry a tire gage and a 12v compressor.

Warm blankets and cell phone

This being winter, even if you stay in motels enroute, some warm blankets will make a breakdown a lot easier to take. I carry a dual-band phone on all longer trips. In analog mode, I can get out on it most paces.

Miscellaneous

Not knowing the condition of the trailer, I don't know whether you will be camping or staying in motels. A campground guide can be handy, but I seldom drag one along anymore.

Throwaway plastic gloves, especially if you will be dumping tanks.