I would be Happi if they had the Happi brand one again. I got the smaller one when it was offered here ($50) and I really like it – digital air quality sensor seems to work and controls fan in auto mode – when I tried to fluff an old pillow, the digital readout from the purifier started to go up and eventually the fan kicked to a higher speed. After a while air quality number was down again (low number = better) and it’s very quiet. The black model is still on SideDeal for $60.
There was a larger model once sold here but doesn’t seem to be available anymore. SideDeal has the filters for it for 3/$99, but you can’t buy the larger model as far as I know – would actually pick one up based on my experience with the smaller one.
Sorry to go on and on about a different product – I don’t know about the Shark one but based on info it seems like this one is pretty good for the $, and availability of 3rd-party filters at a reasonable price is good too.