We can find Product to sell from :

Affiliate merchant site

Actually we can register to join an affiliate directly from affiliate merchant site. to find affiliate program , just typing in search box in search engine followed with "affiliate" or "affiliate+program".

Example :
We want to join with fishing affiliate program, just type "fishing+affiliate" in search box at search engine site

Affiliate Provider site

Affiliate programs providers is third party that prepare databases, affiliate IDs, affiliate links, link-tracking also payments services to various affiliate merchant.
Through affiliate providers programs, we can finding products more easy and faster. every affiliate programs providers represent many affiliate merchant.