Screw Plugs for corner light markers

So I bought some new clear corner lights for my B2600 and when I took the originals off I discovered that both the driver and passenger side top insert plugs that hold the marker light assembly to my grill were missing. So they only screw into the bottoms which doesn't make for a very tight fit, which explains why the old ones were so nasty. Anyway, does anyone know where I might be able to buy a couple of those plugs anywhere around? Any info would be greatly appreciated. Thanks.

Uhhhh.......Junkyard maybe?

Automotive paint store? Ace Hardware?