Battery pathlight moisture

I have 12 Pathlighs and this spring I decided to replace the D batteries. To my surprise 4 of 12 had water inside the battery compartment and condensation in light lens. There are no cracks in the case. When you remove the stake there is plug/seal (?) in the battery case. It was soft and when I squeezed it water came out. I left them in my house overnight “drying out” and to my surprise this plug became hard and dry. All my Pathlight battery lights are working well. The only thing I can replace is the nylon O ring. I need a part number or show me Amazon link.