I won't claim to know all the new consumer stuff that keeps coming out, but I'm not aware of anything that's both a smart switch AND a motion sensor... I think you'd need to combine two parts to accomplish that - a wall switch combined with a separate motion sensor. The good thing is, the occupancy sensor for the office could be placed where it does a better job of seeing you. That said, most motion/occupancy sensors have trouble detecting someone who's pretty stationary so you'd need to make sure the timer is long enough to catch actual movement.
You could look at dipping your toes into Home Automation with z-wave and any of the available controllers, like SmartThings, Hubitat, Vera, etc.. then get a z-wave switch and add on the motion sensor. You could also leave the switch always on and use something like Hue bulbs with the Hue motion sensor - but if the switch gets turned off, it all fails. Stitch by Monoprice.com has motion sensors and switches too and doesn't need a hub. I have no first-hand experience, but it looks like you could probably pair a motion sensor and switch quite affordably with that too.
