Hello forum!

I have recently found something that bothers me quite a bit about my car. My a/c on and off has made this rumbling noise and so I took it apart and pulled out the fan from under the passenger side glove box compartment. So far so good, changed the filter while in there and the sound was due to a million leafs lodged in the fan and also the filter.
After further examination I noticed that under the hood, on the passenger side, the little rubber cover is missing allowing leafs to clog the drain but most importantly, that's how they get into the cabin.
On the driver side, there were some leafs in there too, but not nearly as many as that cover is keeping them out. I don't know how to explain what that cover looks like so I will just post a couple of pictures.
I assume it would make sense to take off the whole piece, surrounding the windshield wiper arms in order to clean under there. If you have instructions for that I'd be happy, but I'm sure I can find them through the search function.
So my most important question is, what to do about that missing cover? I know even though I cleaned everything up and the a/c fan runs as smooth as ever, I will have the same problem again as leafs will flow down that area under the hood again and reach the cabin through there.
I'm grateful for any ideas!

Thanks a bunch as always. The forum has been awesome and you guys usually come up with great solutions so I figured I'd ask.
Please see pictures below!

Nick