There to find bloggers that want to blog about products/services to win prizes?
As usual, Google is your best friend.
Maybe this article will help you to get you started
http://www.crowdfundingpr.org/6-tools-you-can-use-to-find-bloggers-in-your-niche/
Besides Google, Wordpress can help you properly. you can try once.
And how would you do that? I believe @molona; was referring to Google as a Search Engine. Anyways, try searching for blog directories in Google. You’ll definitely find bloggers in your niche.
Yes, I did. Maybe @Maissouna; didn’t read the post correctly and very possibly I didn’t explain properly 
Its okay i have got the point dear molona.
I would recommend one more way to find the bloggers and that is to use the search operators in search engine query box.