Benjamin Olson
Hero
The OP is looking for a Charisma buff spell, but charm person has never been that kind of spell. It's always been a mind manipulation spell. A Charisma buff spell might be interesting though and a question occurs - does that have the same problem as a charm person spell or not?
It does seem like in a 5e context it could be changed to just "Charm", a self buffing spell that gave you advantage on charisma checks with a particular target and gave them disadvantage attacking you, and it would achieve most of what Charm Person does with a fraction of the creepy mind control vibe.