Is there a way to ignore OnMouseDown() if a collider is set to Trigger mode?

Hey there, so I'm making a tower defence game and using a circle collider set to "is trigger" to detect which enemies are in the range of a certain tower, but because of that if I click anywhere in the range of the tower it calls OnMouseDown(), I would like it to only be called when the mouse is over the sprite instead.
 

Is there a way to ignore that specific collider when clicking? The only other work around I can think of is to rewrite the detection system using the OverlapSphere function.
 

Thanks so much for your time!