I am not aware of any single source for cemetery records for Shelby County. That is probably because it has long been a place with a large population (relative to the surrounding areas) and it has a lot of cemeteries. Elmwood Cemetery alone has over 80,000 burials.

I am occasionally at Elmwood (oldest active public cemetery in Memphis) and I will look for the names you mentioned. Other than that, the only way would be to check with each of the numerous cemteries to see if your people are listed.