Ace,
go to a store and buy them firsthand. That way you ensure that you will be able to pay the proper amount of sales tax on the item and help support our comrades on welfare.
Otherwise, if you go to the post office and get one of those "new resident/welcome to the community envelopes they have numerous flyers for personalized address labels in there.
They all have their websites on the flyers too. Or you can do it via snail mail.
I have used a few of them from the various places I lived and never had complaints, although I recently bought a rubber stamper for 7 bucks online with myaddress on it and think its a lot better than getting a roll of 1000 address labels.