KWA products are tune for .25g bbs. if you use .20g you will probably get frustrated to find the sweet spot on the hop-up.
Also, that silver metal barrel looks like it's for the old gas system. The new NS2 barrel is different.
humm... no. It's on KWA ProShop. http://store.kwausa.com/kwaumarexhandkmp7barrelthreadadaptor.aspx
Problem is, KWA ProShop can't service folks outside of US. You have to contact the Helpdesk directly to order one.