Chalkboard stickers got to be really popular a few years ago when chalkboard was all the rage (I mean, every wedding had it incorporated somewhere at that time). But, if your stores are all sold out, you have a couple options. The easier option is to just buy a gift tag pack and use a piece of baker's twine or ribbon to attach the tags to the jars. The harder option is to make your own cardboard "sticker". We actually have a full tutorial on that in our DIY Graduation Cap Mason Jar Craft, if you want to check out that tutorial for details.