I'm going to suggest something. It'll cost you something like $40us. Go to filmspecific.com and sign up. They have some resources to help you deal with sales agents, what to look out for, contract terms etc... oh, and an agency database. Their distributor database may be of value to you too.
In the mean time, I sent you a PM with enough leads to keep you busy for the next month or so.
PS. I have nothing to do with their site/business/whatever. I'm just a fan of the quality of the material they make available for producers and other businessy film people.
I know a couple but the doco world is very specialized. You'll need to hunt for one that is a great fit for you. Don't expect a lot of money (if any). They market is quite depressed. I knew one local travel channel doco maker who had to pay to get it on the air. I'm not sure why he accepted that deal (production value wasn't high) but that's the way the cookie crumbles I suppose.
If all of that fails, I do have another lead for you, however it'd be quite unconventional for you to consider and the chance of them saying yes is quite slim unless you're doing a travel/food doco. Last time I spoke with them (about a year ago), that's what they were mostly after.