1. Bank: Large commercial banks usually provide gold bars with guaranteed quality. The price of gold bars sold by banks is usually lower than the market price, and the quality is guaranteed by the bank's reputation.

2. Large jewelry stores: such as Chow Tai Fook and Lao Fengxiang. These jewelry stores have a good reputation and the quality of gold bars is guaranteed. But it should be noted that the price of gold bars in jewelry stores may be slightly higher than that in banks.

3. Gold trading platform: Some regular gold trading platforms can also provide gold bar trading services. These platforms usually have strict supervision and security measures to ensure the transparency and security of transactions. At the same time, the price of gold trading platform is usually flexible, and investors can choose to buy or sell according to market conditions.