There is nothing sold near Jiuzhou Port, and the things sold in Jiuzhou Port are very ordinary.
There are no Hong Kong specialties sold at Gongbei Port, they are all sold more from Macau.
What specialty products from Hong Kong do you want to buy?
If you want to buy, it is better to go to Hong Kong to buy. Now it is cost-effective to exchange RMB for Hong Kong dollars, and it is cheaper to buy in Hong Kong without tax.
I just came back from Hong Kong yesterday, haha.