I believe the Cake Mate ones do not contain gelatin, but always give the label a check when you're in the store. If you get totally stuck, there's always the option of making a small batch of royal icing (icing sugar and milk of your choice, mixed to a thick consistency) and piping it out of a plastic bag. It'll be opaque instead of gel-y though.
I did think of doing that, but I don't think that there is any way that I could make the lines thin enough that way. We'll see what happens. I definitely will check out the Cake Mate. Thanks for the tip. =]