Here is an idea. On Amazon, you can find vents that have fans built in them. They pull the air from the vent which doesn’t have as much hot or cold air coming out of it pulling the desired air into the room.
AC Infinity AIRTAP T4, Quiet Register Booster Fan with Thermostat Control. Heating Cooling AC Vent. Fits 4” x 10” Register Holes. https://www.amazon.com/dp/B0792QR5YT/ref=cm_sw_r_apan_glt_fabc_RB5E78NDEYFCVV28TRHD