Does anyone know where can be found a secondary markets for such coins? or what the price of exchange is around?
The only likely secondary market will be right here, on this forum. That said, I doubt you will see many appear for sale.
As for the price? Not able to answer your question as we have zero sales to go on, but it's going to be down to whatever someone is willing to sell one for, and what one may be willing to pay.
Thank you for your help. Those coins got much harder to get now that you've got to be chinese or be able to pick them up there. Do we know if they could ship them abroad again in the foreseeable future?
As you said, no one is actually selling their 1/2 btc coins for the moment.