Researching search terms and the sites they return

[Marc A.]

I was asked this question by the fellow in my company whose job function is to market our product to other websites and try to get them to sell our product:

"Is there a website out there that provides ranking information on websites with the highest sales rate when somebody accesses their website via searching for a particular term?"

He is basically trying to contact the top 10, 25, 50 etc. websites who are the most successful at selling products related to ours (cholesterol supplements), and asking them if they'd also like to sell our product as well for a % of the earnings.

I instantly thought the top 10, 25, 50 websites returned in a google search, but after I thought about it for a moment, google returns only a list of the most popular websites based on a search term, not the most successful websites based on a search term.

Thanks for any info you guys/gals might have.