I already have one and she's pretty good size. I don't mind lugging it on board as long as it's allowed.
I have an Amaircare Roomaid that I travel with due to severe allergies. Pain in the butt to travel with, especially flying, but necessary.
Before each cruise I email
DCL Special Services with information about and the specs of the device [particularly the power and power cord], explain why I need it, and confirm that it is allowed on board. Each time they confirm that it is and provide me with instructions on how to get it inspected once we are on board so that it can actually be used.
To be safe, I print a copy of their reply email and carry that with me when we board. We've only had an issue once, which was resolved quickly when I showed port security the email explaining that *I* was to take the device to guest services to get it cleared.
FYI, the device must either look weird or be unusual enough as every time we go through security with it [airport or port] *it* gets pulled for secondary inspection [other things I have do too, but the air purifier always does]. So be sure to package it considering that it WILL get handled by security. And budget in the extra time.
OP, if you don't actually need an air purifier, a small battery operated fan or one of the many smartphone apps would be an easier option if they would do the job.
SW