These days many manufacturers make their electronic products dual voltage (for manufacturing ease) so it is generally not an issue to buy electronic products from the US and ship them with EgapGO to use in HK, you just need a plug adapter.
Any product with a USB plug is automatically dual voltage, so you don’t have to check.
Websites like Amazon and department stores (Brookstone, Kohls, Macy’s, Zulily, etc) don’t usually document the voltage in the product description, as they are catering to American buyers who automatically assume the voltage is correct for them to use at home and are not thinking about using the products overseas.
However, if you go to the manufacturers’ website, you can usually find out easily if the model you are interested in buying is dual voltage before you buy it.
If you can’t find the information on the manufacturer’s website, you can email the manufacturer’s customs service team (or chat with them online), and they will let you know.
As a final observation, even if the product you want to buy is not dual voltage, voltage converts are not expensive, nor very big these days. So if there is a particular brand/model of electrical product you want from the US, you can still buy it in the US, ship it with EgapGO and use it here.