I joined a campaign and one of the subclasses for artificer was a tattoo artist.  I found this really cool. Which book is this in?

this sub-clase maybe is a homebrew creation.
de magic tattoo it's like a scroll

You COULD take the “Painters Supplies” and re-flavor them as a tattoo artist’s kit.

Actually, that’s pretty nifty. I might put that character idea in the bank.

"Tattoo Artist" is the (un)official sub-subclass of any Artificer that takes "Replicate Magic Item: Spellwrought Tattoo" as an Infusion.

...At least, that's my personal headcanon for this. Otherwise, you're gonna have to rely on flavor-brew, in order to make a Tattoo Artist Artificer.