Most years, we take the RV on a road trip of one or two months. The obvious stuff to bring includes extra prescription glasses, plenty of prescription drugs, a stash of cash etc.
Some other misc. things I like to bring are front & back copies of our credit cards and insurance cards, copies of passports along with the originals if you might cross a border. Copy of home insurance policy info & agent contact. Copies of the dog’s records especially rabies certificate (had to produce it at a NY State Park once).
I once lost a tooth crown in the middle of nowhere, and since then I carry a little container of temporary glue goop from Walgreens. Also eye drops and an over the counter eye ointment my eye doc recommended after a minor eye scratch. A little kit to repair eyeglasses. A thermometer and common over the counter meds like cough medicine, laxative, anti-diarrheal, chapstick, NSAID, etc.
Extra drinking water filter for your RV if you use one - we have encountered some bad local water with sediment and off taste, and bottled drinking water jugs for places with boil-water advisories.
Extra DEF for diesel people. A lot of the stuff listed can be purchased but we like to stay in state and national parks which are in the boonies sometimes. I smile when I recall the clerk at a Walgreens pharmacy back home who told me I didn’t need a 90 day supply, I could just go to the Walgreens in Yellowstone.