Spare parts and equipment

One thing I had to use twice: Tire Plugs. I had a flat tire right in the middle of Denali Road in Alaska, pretty lonely, the moose did not take any credit card! And one time south Texas at Pecos River, no garrage in this area. Bring many plugs, sometimes you will need 3 or 4 to plug a hole.

A few things I think is important: nuts, bolts, screws, standard tools, a voltmeter, PB blast penetrant, boost cable, pry bar, big hammer, repair tape.

Out of maybe 15,000 or 20,000 parts you won't pick the one that may break. If you have been doing good maintenance all along you won't need anything but a cell phone and a credit card as said above.

I carry the same items all the time, whether on a trip to Alaska or other places. Usually I carry a replacement filter for each one on board, oil, fuel, air, etc. and the needed tool to change them. I don't plan to change the oil myself on trips, but it is handy to be able to have the correct filter if the shop that is doing the change doesn't have one. I also have a nice selection of electrical fuses, small nuts, bolts and screws, spray lubricants, few extra quarts of motor oil, grease gun and tubes of grease, 12 volt air compressor and tire plugs appropriate to my tires, tail light bulbs to fit my rig, a three foot length of fuel line, and some tape, duct or gorilla, good glue, some caulking, small tube, faucet washers to fit, water filters for the rig, and all this fits in a standard sized milk case.
Seldom need any of it but nice to have if needed.

extra fuel filters and know how to change it. a roll of duck tape , a spare surpenteen belt also.

A cell phone and a credit card........because no matter what you take it won't be what you need.