Rocks! You should be able to borrow a few rocks almost anywhere. You can bench them, overhead press them, clean them, snatch them, squat them, throw them, jump with them, swing them, even curl them. If you are with a companion, he or she can place a rock on your shoulders to do weighted push-ups, or place it over your sacrum for weighted planks, or on your waist in front to do glute thrusts.
And if you carry a short piece of rope, you can throw that over a branch, a beam, a swing frame, and do pull ups. Google "rope pulls".
Our greatest fear should not be of failure, but of succeeding at things in life that don't really matter.--Francis Chan