Hi webmagnets,
Yep you got my attention with the 'steal' word. Not in a good way though.
What other affiliate managers typically do is a Google search for company name of the affiliate program
you are targeting. For instance if you search for Irv's Luggage, a lot of the top results are going to be affiliates. You need to search the pages to be sure they are affiliate links, then try to find the contact info. If it's a big popular brand like Walmart, you'll have to wade through a lot of news stories and stuff to find the affiliate pages. There is software that can help you automate the process to some degree.
Once you have affiliates you want to contact you need to proceed with caution. Many affiliates consider recruiting emails to be spam, because you really are sending then unsolicited emails. So the only way to do it is to really take your time and personalize everything. You need to use their name and site name and say something that sounds 'real' not like a form letter that reads as if you generically sent the same thing to 500 people.
I never do email recruiting because of the reasons above. You could also try to call them. More time intensive and some affiliates don't like phone calls either, but that's another option IF you can find a phone number.
Hope this helps and best of luck!