Mouser has the Adafruit PMS5003 in stock right now.
https://www.mouser.com/ProductDetail/Adafruit/3686?qs=rrS6PyfT74ekfI0ilCENKA%3D%3D
https://www.mouser.com/ProductDetail/Adafruit/3686?qs=rrS6PyfT74ekfI0ilCENKA%3D%3D