I just happen to own Journey to the Edge (Koala Lumpur), Bad Day on the Midway, Normality, a demo version of Shadoan and Dark Seed I (but not DS II)!
The only other games above I'd be interested in would probably be Private Eye and The Dame Was Loaded.
Most older games I usually either find at Value Village (the Canadian version of
Savers) or am fortunate enough to get on eBay. You really do need to be persistent (and a bit lucky) to be able to win adventure games on eBay. One drawback I face is the sometimes insane shipping costs US sellers charge for shipping to Canada, which can be higher than shipping from the UK or Europe!
Games I got on eBay include Reah, the Discworld games, Noir: A Shadowy Thriller ($0.99 + $13.99 shipping!), The Bizarre Advs. of the Woodruff & the Schnibble, Byzantine: The Betrayal, The Quivering and Obsidian.
I bought The Neverhood at Value Village for under $5 (jewel case with manual, no box)!
Lotsa luck trying to get
that on eBay cheaply!