Found it
Don't know if you are still looking but here's a link to an OEM spec replacement black rear bumper withoiut reversing sensor holes for $308.
Rear Bumper - Auto Parts Warehouse
REFLEXXION PRETENDER SERIES STEP BUMPER ASSEMBLY, BLACK -- 79 in. length; 17 in. width; 10 in. height; Includes pads, brackets and light kits; Without sensor holes; Made from tough 11 gauge steel for extra strength and durability; V5 rated; Features OEM style for exact replacement to a damaged stock bumper; Provides dress-up styling, reliable rear-end protection and step convenience; Made in the USA; Easy installation; With Reflexxion's limited warranty.
Material: Steel
Color: Black
Warranty: Reflexxion's Full Warranty
Location: Rear
Fits 2005 Nissan Titan All Submodels; All Engines;