The decals from Pinball Rescue will make your search easier. You could even use one from a later game like Meteor etc that had a different design. Spray it white and apply new decal.

You could buy this off Mark.

http://cgi.ebay.com.au/Trident-playfield-with-parts_W0QQitemZ380134179942

Has the apron, plus you'll be able to use some of the other hardware for your game. Then re sell the playfield once you have finished with it.