You can use services of e.g. OneNow (www.comgateway.com) :
Buy online, then ship everything to the US address offered by OneNow, thne ship back by courier (DHL).
This way, the courier charges for US ==> HK is around 25% to 50% of cost of items you buy.
OneNow is a Singapore company, everything is done online and you pay by Visa.
I have used them several times ever since end of 2008.
There are a few other companies offering similar service.
I also found a yahoo.hk "seller" offering such service, but not sure if it is reliable.
You must know the cost of what you buy very well, otherwise you can find the same items cheaper in HK and it will not be worthwhile to buy online and ship back.