For those with early solid state games from Williams, Gottlieb, and Bally which use a 6 inch full range speaker, they have been hard to find at times. I've found an excellent replacement at Newark (formerly MCM Electronics).

It's 6.5 inches but the mounting holes all line up with 6 inch original speakers. This is full range, 8 ohms @ 50 watts. I just put one in an Eight Ball Deluxe and it fit & worked perfectly. So crisp and clear is the sound now. We just bought a dozen of them because the price was so good. Each speaker was individually boxed too. We paid about $6 per speaker.

Newark # 95Y2940 or MCM # 55-5690.