Thanks for the quick response! I checked out the location of the part number you suggested on my bike. That bracket holds up the two red side reflectors. It sits above the rear wheel but behind and inside the rear fender.
The perspective of the exploded-view rear fender shot on the TGB Web site is above and at an angle to the assembly. If you were to view the assembly head-on (i.e., looking at the bike from behind), you'd see the four holes in the fender, which reside below the rear reflector assembly (part 458015).
My guess is that, unless TGB uses that fender on one of its 151 cc bikes, it will not have a license plate bracket available because 50 cc bikes do not need to be registered in most (if not all) states. If you can find something, great. Otherwise, I'll try to call Cobra on Monday.
Rod