JS Digital US via Amazon has JSAUX USB-C to 3.5mm Female Headphone Jack Adapter for $6.98 - $3 w/promo code AUX2USBC at checkout = $3.98. Shipping is free w/ Prime or on $35+ orders.

Features:

• The USB C to 3.5mm audio adapter features a Smart DAC chip. It is low power consumption, excellent and stable decoding performance, and maximum support for 16Bit/48Khz audio sampling rate. The DAC chip can also convert digital audio signals to analog audio signals and keep the original sound quality of your headphones. The 3.5mm female port compatible with CTIA
• This compact usb c to aux adapter can connect your usb c devices without audio jack to headphones, headset, speakers and other audio devices. Call, volume control, pause via function keys on the headphones are possible