I recently stumbled upon Publons, a social network of peer reviewers, with a database of potential reviewers, along with their areas of expertise, stats, and contact details. I wonder if there are more platforms like this? Can we make a list of serious websites dedicated to reviewers or peer review? If there are some specialized in Mathematics, I'd like to hear about them.
I don’t think Publons provides what you’re searching for. If you’re looking for potential reviewers I’d suggest you to look into F1000, PeerJ, Peerage of Science.
The latter I’ve come across with a while ago, see question below.