“Barding” refers to the armour and ornament on a medieval-era horse:
Here’s an example of barding from Germany, circa 1537, also with instructions for making your own.
If you’re not the crafty sort, Hightower Crafts has medieval-style saddles, stirrups, barding and chamfrons (heavy leather masks attaching to the bridle).
If you’re not into the re-enactment scene, you could (with a few modifications) have a way to transport donuts and spare horseshoes on those long trail rides:
Check out this spettaculary set from Mansour Designs:
Finally, Brad Gorby at Geeb-o-rama takes us through the making of Breyer horse barding: