Yes, these days there are more freelance people out there. You're looking for someone who has the experience in being independent, works at home and likes it that way, and will probably want base pay plus commission.
I don't know many people who are willing to sell in this environment for 100 percent commission, especially taking on a site that hasn't had a dedicated rep before. Even if you could find that person, they would bail out as soon as they can find something stable somewhere else.
Regardless of the compensation plan, you might be paying out 50-100% of the revenue in compensation in the early months until that person is established, then drive that percentage down toward about 30% of revenue as the sales grow (hopefully).
Before trying to find a rep, you might consider looking for higher-level agencies that will represent your site. Whether they will work with you depends on the niche and the audience size. Travel Ad Network, for example, would work with a site of your size if you are focused on travel.
But I would still encourage you to consider using AdSense, even if they don't reveal their share. It's higher quality filler if nothing else, and you can bump it out when higher cpms come along.