Part name and number?

They are called "plastic push rivets."

Here's an example;

20 x Plastic Screw Fastener Rivet Clips Toyota Mazda | eBay

I believe that they are 7mm. I like the screw removal ones, because they hold better than the OEM ones.

They use the standard ones, because it takes a little more force and more time for them to push the "screw removal" ones on the assembly line.

 

They are worthless as a fastener. Once they are removed, using them again leaves them loose and they can fall out. Even from the factory they are pretty loose. Essentially a disposable fastener. My independent Toyota mechanic tells me that the factory often changes the fastener, and you never know what's going to turn up in there. They're so cheap, apparently Toyota never bothered to standardize them. Pretty aggravating, and you might consider finding a different fastener. It only needs to fit the hole.

 

The "screw type" hold up a lot better. Pushing in the crew is like a "wire tie" ratcheting action on three sides of the screw.

You can't remove them by pulling the center out. Because you have to unscrew them with a Phillips screwdriver, they hold for years.

I have them on 15 year old Mazdas and they still hold.

The reason Toyota went to the weak ones is because of production cost. The screw type takes more time and force to install. That costs money and more strain on their workers.

I've replace ALL of mine with the screw type. The friction type doesn't hold the under panels securely.

Those holding the "oil change door" are legendary for coming off and causing the door to drag on the road. Many "oil change doors" are lost and become expensive to replace.

 

IIRC the cover is called a radiator apron or cover.

SCH-I535

 

When it has to hold, I use "Nutserts" or threaded inserts that crimp into sheet metal holes like "pot" rivets.

This is the method that is used for side mirrors and car top carry rails both at the both installed at the factory and in the aftermarket world.

They are very often used on race cars.

 

"pot" rivets are only legal in a few jurisdictions though.

SCH-I535

 

I said "NUTSERTS." They are all legal, since a full screw is used to hold the panel.

 

Its "pop rivets", not "pot rivets".

But I'll say it again: don't bother trying to find the OEM fasteners, they're not worth the trouble. Get something better like what's been suggested.

 

FWIW, I got some of those (reliable seller, fast shipping)
They fit OK on the 3 shroud holes. Although they don't really "tighten down", they are vastly superior to the OE fasteners.
Recommended. They don't pop out like the originals with moderate force pulling on the shroud.