Panzertax

Today my neighbour gave me his old vectrex game consol. I have been facinated by this since I was a boy. Now there are one controll and it works ok. its a bit problems with the stearing and firebutton. But since it has 2 player i want one or 2 new controls. Now I dont know how to build/convert a control. But can I buy from somewhere? And if so how much does it cost? I would VERY much appreciate if someone could help me with this.