I made my own! We had about 40 guests, so I made only about 30-35 invitations. I bought a rubber block from the craft store, and used a carving knife to carve images of different kinds of leaves. I went to an online stamp company to get the wording made. I stamped them all on thick water color paper, and used little tiny brads, and paper to make the little flowers on the cards. Then I included a scanned copy of a collage that I made (not shown) that was our map of how to get to the church. We also included written directions, and some people also got hand made invitations to our "unrehearsal" dinner. In the envelope, everything was wrapped in a pretty, and lacey rice paper, and tied with a ribbon.
My advice is to first find an envelope size that you like, and make sure that everything will fit into it. Otherwise you might end up having to make your own envelopes.
As you can see, I also carved this wooden sign for the reception entrance to kind of match the invitations.