Ebay offers Yoto Headphones for $12.99 (reg. $29.99) with free shipping. 

Product Description:
•The Yoto Headphones: Perfect addition to the Yoto player (or any kids speaker) with daisy chain feature so two can listen at the same time with the same speaker.
•How it works: Pop the headphones in the speaker and start listening to your favorite tunes or immersed in your favorite stories. Volume limiting making it safe for kids to use.
•Tech specifications: Speaker driver: 40mm · Impedance: 32 · Audio level: 85dB +/- 3dB · Cord length: 1.5m · Cord material: Fabric · Dual port: 3.5mm stereo · Net weight: 250g
•In the box: One set of headphones with a braided cable that has daisy chain feature, and a soft cloth travel bag.
•Yoto Player and cards: Child friendly interactive audio and cards are sold separately
•What is it: Yoto Player (sold separately) is a carefully connected speaker. Made for kids, controlled with physical cards and playing only the audio content you want them to listen to. No Camera. No Microphone. No Ads.
•See description for more information