There is no such quality described as the soprano register used in the context of the answer above. Soprano is a vocal fach and the registers refer to the breaks within one' person's voice included with the notes a particular person can sing. A soprano and mezzo, even a contralto could actually have the same range. It is the breaks in the voice, timbre, and the quality of the voice that determines one's vocal fach.
Pop singers do use their head voice more often than people think. The head voice isn't extremely high in the stratosphere in one's register. The difference in pop is that singers try to chest their head voice too often. Also I wouldn't be so quick to call Pat Benetar or Christina Aguilaira (sp) sopranos. Being able to hit high notes does not constitute them as sopranos. These two singers have lower female vocal fach qualities to their voices but they have wide ranges. To determine this, you might have to listen their breaks as well during a vocalization, but those two could pass for lower vocal fach singers with high ranges.
There are some pop soprano singers I can steer you to. Disclaimer. This does not mean I like their SINGING or that they are good singers. Ok. here goes.
Gwen Stafani chests alot, but she is a soprano if you really listen to her. Christina Millian, Madonna, Janet Jackson (she sounds more in her comfort zone in her upper register), Mariah Carey, Leona Lewis, Jordan Sparks, Whitney Houston, going further back is Diana Ross, Aretha Franklin, All the girls from EnVogue (except perhaps Maxine), Kelly Clarkston, Ashanti, Fergie, and the media hyped Britney Spears.
Again, some of these singers I would not call good singers, but they are sopranos.
I hope this helps. Also, you can go outside of pop and find some sopranos you might like. The lead singers from Evanescence is a soprano. I can't begin to start on famous classical sopranos. And the bottom line is, most females are naturally sopranos anyway. Most females just don't utilize their upper register high notes as classical singers.
Professional singer/teacher/grad student