I agree with the Texas A&M wildlife job board and Ecolog. Primate stuff is hard to come by unfortunately, and I've seen the South Africa and Peru positions I think you're considering. In general any internship that I have to pay for makes me suspicious. An alternative potentially would be to work with other taxa that have qualities that are in line with your general research interests. Other highly social species for example. When you write your SoP for admissions, or when you contact potential advisers, you can draw on this experience. Having one field experience in the bag may help you net other primate-related projects. While some project leaders like their interns to come in with a lot of knowledge of the species or regions in question, others really just want to see that you have the skills necessary to work in the field in general. Having worked on completely unrelated projects but in remote areas or in difficult conditions with small groups/long hours/detail-oriented tasks might be enough to get you a future internship that is exactly what you're looking for.
