Amazon Essentials now goes up to size 15 in some styles. I'll edit and post the link when I find it.

Edit: https://www.amazon.com/Amazon-Essentials-Womens-Ballet-Mauve/dp/B082PN79QX/ref=sr_1_4?keywords=womens+size+15+shoes&qid=1637708868&sr=8-4

https://www.amazon.com/Amazon-Essentials-Womens-Belice-Ballet/dp/B07PNY4T2V/ref=sr_1_2?keywords=womens+size+15+shoes&qid=1637709058&sr=8-2