You can just use "Google" to see if there are any local caregiver support groups in your area. That's how I found the one I belong to in NC. Good luck!
Many people with this syndrome have dementia caused by either LBD, AD or Parkinsons. Because it is associated with dementia, you might try a dementia support group. Although I doubt if anyone will specifically be there for Capgras, because it's a rare affliction, the delusions and condition of anosagnosia is common with many dementia diseases. Call the Alz Assn to see where a support group may be meeting near you. I don't know if they're still virtual, some may be live now. Maybe your local Area Agency on Aging can help.