because the original buttons does not fit the aluminum

When you say "original", do you mean the oddly-shaped buttons of the Mk2 players?

Or do you mean the original buttons that came on the Mk1? Those are small round buttons that fit on the button caps, they are a standard Farnell part. I thought your face was designed to accept those just from the looks of it.

The nice thing about the farnell buttons is that you can get translucent versions, so you could theoretically have the lit buttons and the aluminum faceplate.