Here is the link to the exchange https://wallet.counterwallet.io and it's free to sign up. There are two ways you can purchase XQNPSFUND asset by XCP
or XQNTOKEN.

XCP more information http://coinmarketcap.com/currencies/counterparty/#markets

XQNTOKEN more information https://bitcointalk.org/index.php?topic=1195335.msg12989353#msg12989353