Service2worldwide via eBay offers the Rotating Smartphone / GPS Car Mount for 99 cents with free shipping. (Hittime_3c via eBay charges a few cents more.) That's tied with last week's mention and the lowest total price we could find for any such vent mount by $4. It features a rotating clip that attaches to most air vents. The color will be chosen at random

Note that this item ships from China with an estimated shipping time of two to seven weeks.