Suarez...unavailable and a c***
Lewandowski...unavailable
Bale...obscene wages for a crock
Costa....c***
Mbappe....unavailable
IMO Guardiola won't ever buy a pure 9, he doesn't like one-dimensional players. And if you watch his teams playing, it simply contradicts his philosophy - it's akin to handball - pass the ball aroung the box, then attack from unexpected direction. Besides, such approach ensures that you have enough bodies behind the ball to press immediately after the ball is lost.
So, guys like Icardi, Kane, Lewandowski, Costa, Balotelli etc. are out of equation. Using them in a team that defends from the front is like playing with 10 men, you need someone either to comfortably drop to midfield, creating numerical superiorities, or to be effective all across the front line, searching for channels and occupying defenders. Shevchenko, Messi, Henry, Gabriel Jesus, Mbappe, Martial are good examples. Griezmann and Werner (I'm reading that he's good on the wings, is that true?) more or less fit this description.
Even when Pep only had Mandzukic, he forced him to play him in a 'Van Basten way', roaming across, dropping to the wings and engaging in quick combinations. Sometimes it looked hilarious. Now he does it to Aguero, who was a selfish finisher all his career.
Forward like Kane would score billions of goals but wouldn't necessarily make the team better as a whole.