Nope, Internally in my message meant sticking in something from the outside to block off any air from coming inside. Looking at the photo, you could get something slightly oversized, manouever it inside the vent hole and then use the exising screwholes to run in screws to pull it tight against the inner wall. Or if there were no holes available to secure, same idea but run a large bead of sikaflex on the perimeter of the blanking panel and pull the panel hard against the inner wall.
(if wondering how to pull a panel from the 'wrong' side, couple of screws around the middle area and use them as handles, then once adhesive set, remove screws and dab some sealant in the screwholes left)
I know what you mean about clearance and fridges.... When I was removing my original 3-way fridge, the clearance through the habitation door to take the fridge out was so tight even after removing the door seal, as the fridge was coming out the door, the sticky product label on the side of the fridge peeled away as it slid against the side of the hab door frame