I suggest that you apply for summer undergraduate research programs in the United States if you haven't done so already. They are more established and have the funding to provide you housing and living stipend. The more competitive programs even have money to take you out for social excursions and travel.
I'm not aware of any summer undergraduate research programs overseas. The international summer programs that I have seen have all been taught courses. What you can do is e-mail P.I.s overseas and ask if they have any temp openings for summer research. Although, you most likely won't get a stipend like summer undergraduate programs in the United States. I'm at Cambridge Univ. and no one in the building knows of any summer exchange research programs.
I've participated in Baylor's SMART program and NYU's SURP. They both are excellent summer programs located in two great cities. Look into those.
If you want international experience, I suggest that you participate in a one-year MPhil program at Cambridge or Oxford. Good luck on your search.