I am engaged in this line of work. Personal advice: for convenience, you can browse the Internet to compare the local electronic components market. If you don't mind long-distance transportation, you can go to Huaqiang electronic network, love procurement, Lichuang Mall, Yaogan network, Alibaba 1688, positive energy electronic network and so on these official websites...
You can inquire about and purchase electronic components. If you are in The Shenzhen area, you can also go to shenzhen, Guangdong Province, Futian District Huaqiang North electronic market, where a large number of electronic business, but the authenticity of the proposal to inquire clearly and then order to buy, or ask professionals to identify in time. Have patch capacitance inductance, magnetic bead demand, can also refer to the official website of Jinqilin.
Buy electronic components, to see which components you need, such as passive parts or active parts, and then according to the cost budget of the case, choose what brand, etc. Will make a different choice.
Some choose to cooperate with the original factory, and some choose to let me cooperate with the single company. Both modes have advantages and are not easy to control.
The most important thing is to communicate more in order to buy the most suitable brand components.