There are several primary places where you can find good market research services. Quirk's Media is an excellent source of global options. Other places match you up with the right service. Professional organizations like the Market Research Society(MRS) are a good bet. You can get good suggestions from colleagues and even recommendations from other business people in your network. Local directories can also point you in the right direction. Remember, you'll need to vet any candidates. Asking to see case studies is an excellent way to review their capabilities.