Drying your own citrus peels is ridiculously easy AND very cheap to do. You'll need a decent citrus zester - such as OXO Good Grips Lemon Zester . The Good Grips brand is an especially nice one to use if you have Arthritis, as the grips are larger and easier to grasp.
First, ensure that you've properly and thoroughly dried the citrus fruit you're going to dry the zest of. (I like using baking soda and water -- make a paste of it and use to really scrub the outside of the fruit.) Wash the baking soda residue away and then remove all of the outer layer of zest from the fruit. Leave the white pith behind - it's bitter and doesn't have essential oils in it like the outer layer of peel does.
Lay the citrus zests out on a parchment lined cookie sheet for a few days - especially great laid out in a sunny window, as the sun will help dry the peelings even faster. When the peelings are totally dried, pour into a jar and keep for your baking. Easy, and delicious!