Personally, I'd say Easyship is your best bet for something like this.
They're not only based in Hong Kong, but have the most robust fulfillment support of any shipping platform IMO and also integrate with Amazon seamlessly. Their pricing structure is definitely the most competitive too overall.
Many order fulfillment companies in Shenzhen or Hongkong have no requirement for order quantity or monthly spend. I have been working with NextSmartShip. No min storage requirements, no compulsory stock keeping units. no monthly order commitments. No minimum charges. Pay as you send. Plus 90 days free storage for each batch of inventry.
I have used Stork-up for over a year and have concluded it is beyond terrible. Highlights are I had set instructions on where to ship a order to the US contact. The HK contact overrode it and had it sent to HK instead of China.
They are very difficult to communicate with, with lost emails and on followups. But they are very good at emailing all of your email accounts you have EVER contacted them with when payment is due.
Patrick, upper level manager, actually threatened me, saying "I know where you live" via iMessage, when an invoice became overdue. We were going through some hard times then.
Needless to say, I am no longer with them.