Have you spoken to anyone at Steam or GOG or the like and just asked them for a list of Indie games that don't sell? Obviously, one reason they don't sell is that they're bad games, but if you can filter those out, then you've got a pretty decent list of developers that are probably looking for another revenue source.

I like the idea! There's clear value for Indie devs who need a sweetener to get people to play, and there's clear value for gamers that like to try a lot of different games but need to control costs.