I notice you can get +4 CHA from a clean suit (+2), formal hat (+1), and sunglasses (+1). (These apparel names are not exact.) I wonder if you can get more. There are a lot of items you can wear at a given time: undershirt (long johns, vault suit, etc.), separate arm pieces and leg pieces, chest piece, helmet, goggles -- that's eight pieces already. Surely not all pieces would give you charisma, otherwise your CHA would be through the roof. So is +4 the max from apparel?

I know graqe mentats gives you +5, but I'd rather have something I can use all the time, any time.

I use the Vault-tec paint scheme for my power armour to get +1 to CHA. Power armour overrides any gear you are wearing underneath though.

That's about right, OP - suits, dresses and some other outfits (mostly the 'smarter' stuff - Sweater Vests, T-Shirt & Slacks, etc) carry the +2 CHA. Fashionable glasses and one of several hats (mostly brimmed) will give you another +1 each, but that's all there is as far as I know.

Considering pretty much everyone will hit CHA 6 to get the Local Leader perks for Settlement linkage, those clothes will take you to 10, which will get you good prices and at least a decent shot at most persuasions. You save the Mentats to breeze thru the super-tough persuasions, carry the clothes 24/7 and swap out as needed (I have mine all hotkeyed - wtb Outfit Saving so we can just assign complete outfits to a single hotkey!)

Short answer: yes, +4 CHA from clothes is as good as it gets. Doesn't stack with PA, tho, so it's either +1 or +4.

you can get higher. i got a suit from a quest on one of my characters that had +3 charisma.

http://fallout.wikia.com/wiki/Reginald%27s_suit

so with the suit, glasses, and headpiece, you can get +5 from clothing. it might be able to go higher with legendary drops with additional charisma, but the +5 is the highest from clothing (so far discovered) that you will easily achieve in the game