People seem to think Bony isn't good enough but we're not going to be able to get a better out & out striker to sit on our bench whilst Aguero plays given that our best formation is with 1 up top; the only way we get a top player is by getting someone who can play in multiple positions up top like Aubameyang(winger/striker)/Griezmann(winger/CAM/striker) & play them like Bayern do with Muller then let them fill in at striker when needed.
Barca don't have a second striker, they just move Messi/Neymar into that position when Suarez is absent. Real don't really have a second striker, they play Ronaldo/Bale in that position in Benzemas absence over Jese. Bayern don't really have a second striker they just move Muller there.
We have Sterling who can do that to an extent but he's obviously not at a level where he can be our striker & replace Aguero without it being a big loss - so for me if we really want a new "striker" it should be someone who isn't an out & out striker, it should be someone like an Aubameyang/Griezmann who could start alongside Aguero in a wide position & replace him when needed, that way you're not relying on a fringe player to step up & provide goals.
Won't happen in January though, I think we can cope this season with what we have, Aguero, Bony, Nacho & Sterling can all do a job from that position & can't see us getting anyone who'll improve that until the summer.