Have you tried Facebook for writing groups? I'm in a Xn spec fic writing group there. I mostly observe and try to learn more about the self-publishing process, but I notice that people are regularly trading beta reads. They just post and ask if anyone would be willing to beta their story and nearly every post gets a positive response. The group also has more formal, non-FB critique groups, but you have to pay to join those. I'm sure there must be a FB writing group for your genre.