Have you looked on meetup.com? Or maybe ask the local club if you can advertise on their web site for a lower pace weekend ride to try and draw out other people looking for the same thing.

Our club in Baltimore has a ton of different ride categories and I can always find at least 1 weekend ride that fits my average pace. Oh and most of the people in the group I ride with are 50-60 years old. So far they all ride way more then me