Here's a little larger favor box I designed, that would hold a couple of cookies, or a small slice of wedding cake, or whatever. The box measures 4"L x 2½"W x 1½"H. "I DO!" pops up through a slit in the top. The popup sentiment can be personalized in Inkscape, bearing in mind that there is only 2½" in which to fit the sentiment on the band.
This file is available for free here.