I checked steam.com and gog.com. No go. Your best bet would be amazon or ebay. I prefer amazon. They provide prompt delivery and you don't have to worry about someone out bidding you on an item.
There are open lists of games you can add your votes to for getting your preference added to the GoG downloads. It is well worth the time to visit there and look up any favorites you've had, to put in some more votes on them.
Remember, that in addition to being both inexpensive, and convenient, the GoG promise is to add whatever tweaks are required in order to run the oldies with currently used OSes.