The fabric for these were purchased online at Repro Depot Fabrics. I can't find this particular pattern any more, but there are a few others that would work wonders!
Merriment Design. This design is copywrited. Kathy Beimer, the owner of Merriment Design, asks that you email her if you are going to use this design. Bonus: if you aren't crafty enough, you can contract her to help make these invites! This is a slightly different version of Kathy's original Poppy invite.
See all of Kathy's Poppy-themed wedding items: sewn poppy fabric invitations, sewn return address envelopes with custom stamps, table numbers, guest towels, ring bearer pillow, place cards, sewn zigzagged programs, menu, reserved signs, whimsical flower garland “altar” and bridesmaid’s handbags.
Another bride has made her own version. Click here to see it!