What would be best is looking up grilles for 2004-2005 models. Your '08+ Sport have the same grille shell as the 2004-2005. The standard "H" bar '06+ grilles, there isn't anything available other than billet for mesh that fills the holes. That's probably why you're having a hard time locating a grille insert for your year.
T-Rex Black Billet: 2004-2005 Ford Ranger - Billet Grille Insert - Full Open - Fits all models - 21 Bars - All Black Powdercoat [20660B] : T-Rex Billet Grilles, Car and Truck Accessories
Street Scene offers a really nice mesh insert (pictured below, courtesy of Mykhael Hayes), but you'll have to get a 04-05 grille insert or grille assembly to place them into. They don't offer full "big mouth" mesh inserts like on the 01-03's.
The good news is your grille assembly or grille insert on your '08+ Sport or the '05-06 STX is a highly sought after grille. Making for an easy sell. And for what it's worth, the standard '06-12 grille fits a 26" LED light bar right in the gap between the grille bars. Making for a super clean flush install. Might be something to look into.
Headlights....honestly, it's worth it just to drop the little cash for these...
Clicky: 2001 2008 Ford Ranger Black Housing Headlight Corner Signal Lamps Pair | eBay