It looks like you have an early model (first picture). I do not believe that they ever offered a plastic bumper for the early models. Note that the grill on the truck in the second picture extends down further than the first.
I believe the only way to get a plastic bumper on an early model is to swap over a Pathfinder front clip, but this is not a straight swap either.
Soul's got a good idea I'd paint it too if it's that what you want the first pic is the 1 piece compared to the earlier steel model 2 piece separate design so you would need to change your upper valance