You're not understanding me. If you ask 20 different lawyers who are the most prestigious PI agencies, you will get 23 different answers. Prestige is a subjective factor. There IS no hard and fast, across the board, always correct, answer to your question.

In any case, regardless of the reason you are asking for this information, WE DO NOT PROVIDE REFERRALS. It doesn't matter that you're writing a paper instead of looking to hire one. IT IS STILL A REFERRAL AND WE DO NOT PROVIDE THOSE.