Thousands of affiliate programs.
Type in your niche + affiliate program and voila.

A good one to look into is a brand site that really fits with your niche and do a search for affiiliate. Sometimes they have one but for some reason don't shout about it. It can also be decent commission as well , good luck, Phil

Ps I am never afraid to suggest they have one if they don't!

As Mikael mentions, there are millions of Affiliate Programs out there. You can click on the Affiliate Programs link on the left-hand menu to find a fraction of these. You can also use Jaaxy to find affiliate programs, as well as searching Google for "Your Niche + Affiliate" etc.

There are thousands (if not millions) of affiliate programs aside from Amazon. Just keep going through the training and you will see more examples