Generally, you should be indemnified by the hospital/medical school that will be "sponsoring" your elective. Your best bet is first to find which school/hospital you'd like to set your electives up with, see what their individual policy is with visiting medical students, and then ask whether or not you need additional insurance. If you cannot get insured by the program/school that you want to visit
AND they can't recommend a way for you to get insured
YET they will still allow you to do a visiting elective, you should strongly and wisely consider not doing that rotation at that hospital!
Lawyers go after deep pockets. As a student, that won't be you. While there's always a possibility that you may get called to testify in a malpractice case, chances are that you will not get personally sued (because you are only a student after all and cannot, technically, function without the supervision of a resident and/or attending nor are you fully responsible for your actions) unless you are doing something you really,
really shouldn't be doing, but if I were you I still wouldn't take that risk.
Information about schools offering elective rotations to visiting students can be found here:
http://services.aamc.org/eec/student.cfm
Contact the person coordinating the program you specifically want to apply for. Notwithstanding the above, none of us here will know the specific answer to your question.
Good luck.
-Skip