The best would probably be the incline curs with dumbbells, although looks like you are already doing those.
Are you doing those fully supinated or are you twisting as you curl? If twisting make sure to not just hammer curl them the majority of the way and try to be fully supinated for most of the movement (this will go for any twisting motion on curls IMO). Maybe also try cross body curls in a supinated position as well. O and if didn't notice I think the supination is the important part so when you do those close grip curls make sure it is with a straight bar and not the EZ bar as that will usually result in less supination.
Overall it will mostly be genetics (unfortunately) but that doesn't mean you can't fight that! This made me rethink some of my own biceps training so thanks.