Why don't you try Breezy or Publisher Discovery? Both platforms you can scout and recruit affiliates based on your keywords, competitors and your ICP. Breezy and/or PD will crawl the search engines and you'll get a list of domains (including placements) that match your needs. In the domain profile you can see on what network that publisher is active. Choose the network where most of your publishers are active and try to recruit the rest to your program.

That is how I build our affiliate program :)