Member Referral Plugin?

I am desperately trying to find something that would work for my site. I want to reward my members for bringing in new members. I would like so each person can have a referral link or be able to give their username to get credit for new signups. At the end of a certain time period I can see who had the most and reward them for it. After that I could reset and do again and again. Is there anything out there that does anything similar? Thanks!

Adam

The site this is for is https://www.milpages.com