I need suggestions for where I can buy Christmas package labels?

Etsy.com

If it must be unique, you'll need to make it yourself. Anything from a store is most likely not going to be one of a kind.

Have you considered going to an office supply or craft store to get the components needed to make your own package labels?

Unique?

What I did last year was to locate some reindeer poo in about September so you have plenty of time for it to dry hard, roll it flat whilst fresh and use those special scissors that fashion a crinkly edge.
Hang them up in the laundry room until dry and hard, dust them with sparkles and make a little hole for the string.

If you can't find reindeer poo, try penguin or polar bear.