I have made a similar style bow for a Link costume. I printed out the image of the bow at life size and then transferred that pattern to cardboard. I layered cardboard to the appropriate thickness, gluing the layers of the cardboard together with super glue/CA glue. I then applied a coat of fiberglass resin to the cardboard structure for some rigidity and stability. Once the resin had set, I used Bondo/Automotive body filler to smooth it out. (You could also use Paperclay to make the bow even more lightweight, which I have seen other people do for Prop bows.) Then I painted it up.
No pep required. Which as Cherry pointed out might not work well in this case, since with Pep you would be creating a hollow structure which would have to be filled with some material for rigidity and strength, or you would have to create the bow in two halves which would be glued together, then you would have to hide the seam, and at the point using the image as a template and scratch building it would be just as much work.