K.E.
S., What about doing it yourself. You can get a shadow box or nice frame from Michael's or Aaron Brothers art mart. You can glue it onto another fancy sheet of paper and burn around the edges or whatever you think is tasteful. Add some of those small fake flowers that are in silk or ribbons and put it around the invitation. Or you can ask at Micheal's, Aaron Brothers if they know who would do something like that.
Or you can go to those scrap booking stores and ask someone there to help you I am sure they would be able to help you do a really nice job, they have some really nice decorations as well as paper. I think you pay per hour or something, but you can just ask for some help and ideas.
I think this will be a great keepsake for them.
Take care,
K.