Buying smart wristband from local brands

Hi everyone !
On my coming trip to Beijing, I would like to buy a smart wristband from local Chinese brands such as Huawei, Xiaomi, 乐心....
And I am not good at bargaining, can someone recommend places to buy such product (brand new) with fixed price.
Any local electronic store that will have the smart wristband from above mentioned brands?
Many thanks.