This is a 3D printable hook to hold items on carabiners to be hooked on a car vents, specifically for a Toyota MR2 SW20 vents, but it could fit other models. The sample photo shows the hook holding a CB radio. It has a right thickness to insert sideways and then turn, relatively stable for car movement. However, it will limit the vent movement and hot air may cause the hook to deform.
STL (Stereolithography, filesize: 35.4 KB), 3MF (3D Manufacturing File, filesize: 22.8 KB), AMF (amf, filesize: 69.3 KB)