Coin purchase

Does anyone know someone who sell it coin

Your chances are extremely small. Very few collectors have any coins from Sealand, let alone have one for sell.

I think EBay or other auction sites would be your best bet.

I have tried to find the listing on Numista for Zealand but cannot find any coins listed, although I know I have one.

https://en.numista.com/catalogue/sealand-1.html

Thank you so much, please tell me if someone have information 

Maybe here.  https://www.ma-shops.com/shops/search.php?searchstr=SEALAND+1994++ngc+-pcgs+-anacs&catid=-1&submitBtn=Search&days_new=  

There is a bronze version for sale on E-Bay for $600.

Thank you, so much. I want to purchase the gold version 

Try here maybe.  https://koinpro.tripod.com/WorldCoins/Sealand_Coin_Offers.htm    Good luck!

Thank you so much