If you search for Exar XR-1072, you will at least turn up a datasheet for this one. Some help for troubleshooting if nothing else.
I did find at least one seller for the surface-mount (SOIC) version XR1072CD. How trustworthy I don't know, but I imagine you could bend the legs into enough of a DIP-like shape for it to work. Even if they're knockoffs, a lot of the internal circuitry is documented in the datasheet and a bit of educated guesswork and experience in analog chip design may well be sufficient to come up with a decent clone.