Find a Facebook Page with lot's of Likes within your niche
Click 'Message' on the top-right Corner.
This will send a direct message to the page admin(s).
Introduce yourself (Hi, I'm an Internet Marketer blah blah blah)
Get them on Gtalk, skype or whatever and see how much you can haggle them down to promote for you for a status updates.
This has way higher conversion then purchasing random fb likes etc because it's targeted. People forget marketing 101 sometimes when it comes to these factors.
Is there any particular reason why you need FB traffic in particular? If you go to buysell ads you can get Tweets ( hxxp://buysellads.com/buy/allsites/by/tweets/pn/1 ) from particular accounts, some niches in particular depending on what type of site you run (you can even get them cheaper I'm sure if you physical asked people on the Internet).