Staples, OfficeMax, Office Depot.
Avery makes a large line of stickers and labels of various sizes. You just need to look for a line that has "no residue" adhesive.
Another nice aspect of the Avery line is they provide MS Word templates for each of their paper products that will allow you to print out an individual sticker or a whole page of them. Much neater and more professional than handwritten.
My 2 cents,
Gary