I don't know what you think about this idea but making a little vacuum former isn't too much to whip up with a blank PC board (breadboard) from Radio Shack and some scrap wood to make a box for it and a hole for the shop vac hose.
Carve up a master and pull down your own clamshels out of thin styrene. You might not even have to make a frame to hold and heat the plastic, just keep the sides of the box up flush with the top of the part, tape the plastic down, vacuum it and use a heat gun to soften it up over your master.
You might find other uses as you go along, very easy to make other lightweight detail parts with if you dont mind making simple master patterns.
Mattel Toys used to have a vacuum former machine toy that pop up for 30 bucks or so on eBay which would help out.