I'm not sure where you are, but did you try
http://www.cars.com or the guys at
http://www.classicoldsmobile.com? I found my Delta 88 Royale Brougham at cars.com. I hope you can find it! I didn't find the exact one I wanted, but I'm going to paint it white instead of blue. Don't like the blue.. I know what it's like to be looking for one of these puppies for sentimental reasons.
I ran into a family friend not long ago and told him, "Yeah, I bought a project car!" (because let's face it, it needs work). His response was, "What is it?" "An '85 Oldsmobile Delta 88 Royale Brougham." "...Why?" "It's for sentimental reasons. My Mom had one. And before that, it was my Grandmother's." "Oh.. Okay."
Good luck!