I have purchased butterflies on wafer paper from a place that is banned from any mention here on Cake Central. I can only tell you it's pink and near Cincinnati. That should be enough to find it thru Google.
If you have anyone near you with an edible printer set up, you can download pictures of butterflies, make a master sheet on regular paper and get them to print it out from the edible printer. Cut them out with small sharp scissors and put a thin (and I mean thin) smear of gel of them. I've even been known to sprinkle a little edible glitter on the wings.
Barring that, you can buy gumpaste butterfly "blanks" (all white) and decorate them yourself from www.avalondeco.com
(The same place I rec for gumpaste flowers.)
Another somewhat different and possibly nutso option is the battery powered butterflies from battery powered candles website. I used on of those on a cake once and it startled the crap out of people. You have to hide the battery, so a fake tier on top is great. The butterfly, which looks amazingly real will fold its wings every so often. Extremely realistic.