Hemp, linen or cotton is recommended. Doubles as shower slippers. Perfect second shoes. Fold-away brim hat. Sturdy, comfortable, medium to small size one.
Some backpacks come with a small detachable one.
To hold your daily spending money, traveler's checks, lip balm, etc. The Mini Mag-Lite is a good choice. Bring spare batteries. A lightweight backpack towel or thin, porous dish towel will do the trick. Toothpaste and brush, floss, mini hair brush, razor, soap, mini bottle of shampoo, travel mirror, nail clippers.