I have been looking for Dragon Quest scans far years. Only recently was I able to find the rulebook, a few cards and the fold-up figures though Board Game Geek, but not the Adventure Book, or the rest of the cards. Then I just found scans of everything on a video game museum side called The Museum of Computer Adventure Game History. They have a lot of game books (Lone Wolf, Fighting Fantasy, etc.), video games, some PRG books, and some board games.
There are a number of scanned files, but bulk of it are video game manuals for old games. You are not going to find a lot in the way of RPG or game book scans. Still, its great to finally find all the cards for Dragon Quest, and three great scans of rulebooks!
Enjoy!