damaged diaphragm in right-side airbox

[ftillier]

Hi folks, I changed filters (cabin and engine air) and noticed that the diaphragm at the bottom of the right side (passenger in US) air box (presumably to allow water to drain out?) is damaged (like it got very hot and shriveled). The driver's side looks fine. I haven't found any posts related to this and wanted to know whether it's critical to fix, if the diaphragm is available as an independent part, or if I need to replace the entire air box. Thoughts?

 

[Rover Range]

It's very common for those to disintegrate.
You can find some silicone sheets and cut a new diaphragm.