I have had good luck getting this sort of thing in the states from Big Daddy Enterprises.

http://www.bigdaddy-enterprises.com/

Todd from Big Daddy has kits catered to the early Bally, Williams and Gottlieb solid state games, and ships daily. He's answered a lot of questions for me and I can't recommend him enough.

While he is overseas, and the shipping does add a slight delay, he is dependable and ships quick.