Havertz is the one. Maybe not a striker, but he can play there and Pep isn't likely to want a Lukaku-type up front anyway is he. Think he wouldn't be outrageously expensive plus it would be good to get one over on Bayern and they apparently can't afford him this summer.
The benefit of Havertz is that you can buy him and keep Jesus in the squad. You can play Havertz anywhere in the front 3 or as an 8, and Jesus could play on the LW as well as striker.