I don't want to come across heretically, but I don't quite understand the thing about bag toppers... I personally find them distracting, waste of raw material, and totally unnecessary. Just think that the cost for one topper will easily be higher than for the cookie material!
How about nice little stickers for the backside of the bag? A lot cheaper, a lot more ecofriendly, don't distract attention from your cookie and are also easier to get. And you can work with one size, whereas for toppers you might need several sizes, if you work with different bags
If you really need bag toppers, Cookie Celebration's idea sounds reasonable. Or if you need real large quantities, contact a local printer and ask for an offer. FYI, my company orders them from China, and we pay between 1-5 cents, depending on size. They are color printed and ready cut. But we order several ten thousand per year, of course.