I have a ceiling duct that drops cold air right above where I sit on the couch. This design magnetically attaches to the vent and redicrects the air.  If you use Fusion 360 then you can adjust the parameters of this design to fit your vent.

The magnets are designed to be press fit (no glue) and removable by pushing the magnets out through the hole in the back.

Print Settings

• I printed this in PETG but PLA should work just fine.
• No supports needed