Vapor pads are entirely optional. The only purpose of a vapor pad is to add a scent to the mist that your unit produces.
Vapor pads (HS-1950) are available for purchase at most drug stores such as CVS and Walgreens, as well as at Target and Walmart. Those vapor pads can also be purchased from the Crane website at the following link:
https://crane-usa.com/product/large-vapor-pads/