You need to tell us a bit more as there were several different ones. A picture would help a lot. And, take a gander at this page Exterior/
Exterior Trim & Moulding and then pick the tab for the type of trim you have (Upper, Lower, Wheelwell, etc) and the type of pickup (Regular, Supercab, etc.).
You'll see that there were several types, and several sizes depending on the cab you have. So, if you can work through that and/or give us a picture then we may be able to help you. (I just offered a piece to Hardy in Germany, so that one is out but I have some others.)
Gary, AKA "Gary fellow":
Profile
Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI