Where can I find a sensor that I can place high up on the wall or in the ceiling that is discrete and that I can connect to the room lighting?  I've seen these setups in office buildings and some newer construction outside the US so I'd like to install in my bathroom.  I purchased one of the light switch/dimmer/sensor combos but it is not exactly what I would like.

Any suggestions?

Search occupancy sensor.  You'll need to wire to a relay or contactor of some type.  I'm not an electrician, but this might point you in the right direction.

https://www.grainger.com/product/ACUITY-SENSOR-SWITCH-Dual-Technology-Occupancy-6DXE6?opr=APPD&pbi=2HTF4&analytics=altItems

Search for "Occupancy Sensor".

I use Sensor Switch models.  
There are direct wire 120VAC models and low voltage 12/24VDC models for use with control/alarm panels.
For simple lighting control, the 120VAC models work well.

For lighting control you want an occupancy sensor vice a security type motion sensor.
Automation/occupancy sensors are programmed to trip much more easily, so they are more sensitive.
Security motion sensors are designed to avoid nuisance trips and are less sensitive, so they can produce unsatisfactory results when used for automation only.

Thanks for the information.  I was looking at occupancy sensors but wasn't sure what would fit my needs.  I don't need anything fancy but thought something that tied into my lights would work better than an all-inclusive unit.

Something like this.

https://www.amazon.com/dp/B004QXIMC0?tag=vglnk-c102-20

It's line voltage, and dual tech.  
It uses both PIR and audio.
The audio helps keep it tripped if you're sitting in a chair watching TV and not moving around a lot to keep tripping the PIR.
It's fairly small and low profile.

That one looks good.  Probably mounts like a smoke detector to a 1G box.  Just get a 3 wire romex up to it from the switch, bet it needs a neutral.

The SenorSwitch website has install pdfs.