or anything else that would work more of the inner parts of my pectorals.
The answer you're probably fishing for is cable crossovers and close grip bench. However, there is nothing
that'll work a portion of your muscle.
As with your biceps, your chest is determined by whatever your parents gave you. Now, if you can actually flex your "inner" chest without flexing the whole muscle, then you're an alien, and cable crossovers are a good fit.
Your best bet is to continue to increase the poundage on your compound pressing, and hope your parents didn't screw you over.