I got these on Amazon. They match perfectly.

Handshop 100% Cotton Flat Shoelaces 5/16" - 4 Colors in 40"-63" Shoe Laces https://www.amazon.com/dp/B089GLTCTV/ref=cm_sw_r_cp_api_i_P5YPVNDSBM2JBV409Z24?_encoding=UTF8&psc=1

Amazon