Yes, I would like to know this as well.
Technically, the dealer should just give you the other two.

I think my plate rattles at times under low rpm lugging around, so this is why I'd like to install the two extra screws.

 

I got them from Home Depot. They don't match exactly (as in the built in washers or whatever you call them aren't the same exact size) but in Home Depot they have slide out drawers and two of the drawers (at least in my store) are dedicated to automotive screws. I just took one of the of the screws out and matched it up to the ones in the store - the screw pattern matches and the length was a little longer than the stock ones but still worked. I wish I could tell you the exact measurements but I threw away the bag they came in because there were only 2 to a bag.

 

Okay, I called around today. Looks like subaru only lists the inserts/grommets, not the screws themselves.

I found a part# off an old subaru forester forum post, 59132AA010. I think these are designed for the mudguards.

I ordered these screws, which appear to be shorter than the original screws, but the same otherwise. They will be here next Wednesday and I will post back with an update.

 

Curious, why not just change all four to a different screw?

 

Ordered 4 of the OEM screws I listed.

I have some from the hardware store that will work, but prefer the black coating and washer-head of the OEM screw

 

I grabbed some from Pepboys.. They have the universal kits..

 

they are 3-4mm screws don't have to get dealer ones, u can get security screws !!!

 

My dealer just found random screws in a drawer lol. I would just bring one into a hardware store and buy four matching that look good.

 

Any hardware store should have 4 SS screws that will work fine. I assume my dealer did that as mine don't look like the one pictured above, just regular round phillips head wood screws by the looks..

 

JDM parts only!