If you end up having to make your own, here's my suggestion:
Make a plug from stacked (glued) blue styrofoam (or wood) and glass it, then add the panel lines with tape.
Then take a clear 2-liter bottle and cut the large end off, slide it over the plug and apply even heat with a heat gun to get it to shrink to fit that plug. Cut off whatever you don't need. The shape is fairly simple, so it shouldn't be too difficult for a guy with the skills to finish this kit in the first place.
Good luck and looking forward to seeing your finished product.
-J