Shenzhen Ye Jing Magnetic Electronics Co., Ltd./Youtuo Electronics (Guangzhou) Co., Ltd./Dongguan Mingpu Industrial Co., Ltd./Yiyang New Age Powder Metallurgy Co., Ltd., these are relatively large.
You can go to the website of Big Bit Electronic Transformer. There are information and contact information of inductor manufacturers, as well as supply and demand information in this regard.