Those air freshener is a PITA for asthmatic people.
- L293D, replace it with a DRV8830 or you could use a level converter (3,3v -> 5v)
- Battery. You could use a DC/DC step up converter to convert a one cell to 5v. This will make the above answer obsolete.
- HC SR501 can be modified to work with 3,3 volt, check
https://screenzone.eu/modify-hc-sr501-pir-sensor-to-work-with-3-3v/