Expander Car Cup Holder, Car Cup Holder Expander Adapter, Expander Organizer with Adjustable Base, Compatible with Hydro, Other Bottles in 3.4"-3.8"(size:fit for 3.4). 【Easy To Install】This car cup holder extender can be fixed on its lower half to fill the gap between the cup holder and the car cup opening, improving stability and compatibility.
eBay