Resurrecting this as it seems to be the most relevant place for the question. Is there any mileage in using something like Krylon Looking Glass spray on some plain glass? Pinball 2000 glass is about 4 times more expensive here in the UK!

That's obviously going to be pretty hard to recreate exactly but a mirror tint spray could be applied in more coats where it should be more opaque. I might get some and try it on a scrap piece of glass unless someone tells me that it's a horrible idea.

I had a proper look at my original P2K glass today. It seems to have a pretty solid tint over half the surface and a gradient over the next 6 inches or so. I can't think why so much of the area needs to have a tint. Even so, I'm going to try and replicate it with varying coats of mirror spray.

Sorry for the late reply. The mirror spray didn't work. By the time there was enough in place for a reasonably strong reflection, there was not enough of the playfield visible. It just looked like a dirty old mirror.