A quick look around the Avalon website (praise be to Google) didn't reveal any 12 strings, but if one digs deeper they may be there. It does say that there have been 15,000 Avalons built so maybe there're some 12s among them. There is a custom shop too, which could be the source I suppose. Why don't you try asking around the Avalon Forum?

Nice looking guitars.

Peace, Mooh.