Have you looked on Boohoo? They have a collection just for petite girls, starting at size 0. I have a tiny waist and their skirts fit me well. They always have 60% off sales!

https://us.boohoo.com/PZZ86630-173-12.html

Also,

I purchased a cute white skirt from Amazon for $19.99 Adidas Girls' Sport Skort https://www.amazon.com/dp/B07T7CSY5K/ref=cm_sw_r_cp_api_glt_fabc_GE2P5H85EJPW3YERG43T?psc=1

And another black skirt from Amazon for $26.99: HonourSex Women Tennis Skirt Pleated Golf Skirts with Pockets Skort Workout Sports Hiking Athletic https://www.amazon.com/dp/B07HD6RVPW/ref=cm_sw_r_cp_api_glt_fabc_0S5QH4G15D1KG0CWY7Y5?_encoding=UTF8&psc=1

Hope this helps!