A simple source for paint palettes, re-use old dishes. These are especially great for acrylic (or other water based paints) because you may cover the palette (plate) with plastic wrap and slide into the refrigerator for the next session. I found the plastic cover ups work perfect to cover my plate. These come in a box of assorted sizes and look very similar to shower caps (another source for covering paints). Where did I find the cover ups? Dollar Store.
Wax paper - endless possibilities.... I mainly use wax paper to cover slightly wet paintings for easier transport. I also use wax paper in between layering steps of mixed media or altered book pages. The wax paper doesn't stick to the adhesive and allows me to continue working.