NE570, SA571, not 8 pin though and possibly only in smd now.
The old 8 pin Plessy SL6270 was the go to chip for this sort of thing if you can find any.
I note that BG Electronics
http://bg-electronics.de/shop/produc...23/language/en lists them in smd and there was a whisper a few years ago that a special run of these had been made, so you may be lucky.