From the picture I see you have marked several areas that are leaking or are potential leak spots. I suggest you order an O-ring kit or 2 from Captain O-Ring (
https://www.captainoring.com/store/c80/AmericanTacticalNova ). Another area these Nova Liberty rifles are know to leak from is the poppet. Does your rifle leak air through the barrel? You can check for a poppet leak by attatching a ballon to the barrel and looking for it to inflate some. Unfortunately I am not aware of anyone currently building replacement poppets. Maybe contacting Pyramid Air or Air Venturi will help locate a replacement poppet. Good luck to ya.