One thing that I learned is that when one has a problem with a specific body part that’s hardly an exercise selection issue (unless one’s doing bicep curls for chest of course).
And if it were, why not just choose better exercises? Dumbbell and barbell presses, neck presses, cable flies, Dips, even push-ups and the Pec deck machine are all good alternatives. If you have problems recruiting that muscle specifically, you might want to work on your mind muscle connection first (there are quite some articles here about the subject)…
How long have you been training for? If you aren’t gaining weight but are visibly more muscular, you might be hitting the holy grail of body recomposition—That is gaining muscle weight while losing roughly the same amount of fat.
If you have been training for less than 2 years and your lifts are actually increasing, this might very well be the case.
On the other hand, there are quite a bit of studies indicating that in order to put on muscle mass at an optimal rate, you have to eat at a calorie surplus.
So unless you want to be eating at maintenance for some specific reason, you might want to increase calories over it (usually up to a surplus of 500 kcal a day to begin).