Here are the smart switches we recommend based on your answers:
Smart Three-Way Switch Recommendations
These all require a smart home hub with Z-Wave capabilities. I prefer to use Home Assistant with this Z-Wave USB stick (which also does Zigbee), but there are many other smart home hub options. The Step-up pick below also has a vacancy/occupancy sensor. If you want to keep your existing switch you can use a Z-Wave microswitch like the Shelly or Fibaro. These install behind your existing wall switch and can be installed in three-way configurations.
Preview
Budget Pick 
HomeTechHacker Recommendation 
Step-up Pick 
Product Name
Enbrighten Almond Z-Wave Plus Smart Light Switch with QuickFit and SimpleWire, 3-Way Ready, Compatible with Alexa, Google Assistant, ZWave Hub Required, Repeater/Range Extender, Toggle, 2 Pack, 81174
Zooz 800 Series Z-Wave Long Range S2 On Off Switch ZEN76 800LR, White | Simple Direct 3-Way and 4-Way Solution (Works with Regular Switches, No Aux Switch Needed) | Z-Wave Hub Required
Enbrighten Z-Wave Smart Motion Sensor Light Indoor, On/Off, Vacancy/Occupancy Sensor, Includes White & Almond, Zwave Hub Required, Works with SmartThings, Wink, & Alexa, Smart Light Switch, 26931
Current Price
$29.99
Price not available
$54.39
Details
Budget Pick
Preview
Product Name
Enbrighten Almond Z-Wave Plus Smart Light Switch with QuickFit and SimpleWire, 3-Way Ready, Compatible with Alexa, Google Assistant, ZWave Hub Required, Repeater/Range Extender, Toggle, 2 Pack, 81174
Current Price
$29.99
Details
HomeTechHacker Recommendation
Preview
Product Name
Zooz 800 Series Z-Wave Long Range S2 On Off Switch ZEN76 800LR, White | Simple Direct 3-Way and 4-Way Solution (Works with Regular Switches, No Aux Switch Needed) | Z-Wave Hub Required
Current Price
Price not available
Details
Step-up Pick
Preview
Product Name
Enbrighten Z-Wave Smart Motion Sensor Light Indoor, On/Off, Vacancy/Occupancy Sensor, Includes White & Almond, Zwave Hub Required, Works with SmartThings, Wink, & Alexa, Smart Light Switch, 26931
Current Price
$54.39
Details
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