The Belkin-made adapter costs $35 and is available at Apple retail stores.
iPad Pro - Wikipedia
[Apple MFi Certified] 2 Pack Lightning to 3.5mm Headphones Jack Adapter for iPhone, 2 in 1 Charger +Aux Audio Splitter Dongle Adapter for iPhone 13/12/SE/11/Xs/XR/X/8 7 Support All iOS &Volume Control
Apple now sells an iPhone dongle with a headphone jack and charging port - The Verge
Apple now sells an iPhone dongle with a headphone jack and charging port
Dongle Apple
Apple USB-C to 3.5 mm Headphone Jack Adapter : Electronics
Belkin Lightning Audio + Charge Rockstar - Apple
esbeecables 2 Pack Lightning to 3.5mm Headphones Adapter, Apple MFi Certified, Supports All iOS Devices : Electronics
Lightning was great, actually - The Verge
Apple Won't Include Free Dongles With New iPhones
Apple now sells an iPhone dongle with a headphone jack and charging port
Apple Lightning to 3.5 mm Headphone Jack Adapter : Electronics
Apple's 2018 iPhones are rumored to not include headphone dongle in the box - The Verge