BAA has a limited quantity of some individual plastics for sale. Some of these are often broken, and can be very difficult to find without purchasing the entire set. I highly recommend grabbing anything you need ASAP ...
http://bayareaamusements.com/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=PPI
Plastics are available for the following games:
Funhouse
Medieval Madness
Star Trek Next Generation
Eight Ball Deluxe
Cirqus Voltaire
Addams Family
Cactus Canyon
Theatre Of Magic
Attack From Mars
Tales of the Arabian Nights
Who Dunnit
No Fear
Creature From The Black Lagoon
Monster Bash
Indiana Jones
Indianapolis
Twilight Zone