Think of anything you need at home.
LTS foods, maybe a #10 can of freeze dried foods, ammo is always acceptable, but some people are anti firearm. Usually it is something they have on hand already they don't want/need. Extra propane tank.
We picked up a AR for barter of wife's old engagement ring (previous marriage). What a deal.
You may also look at a service. Mow lawn tree trimming etc. Maybe they have eggs, you don,t. work out a deal for dozen eggs for X number of weeks.
I would throw out some suggestions to them, to give them an idea of what you are looking for.