Ran across this site where someone has written a program for the USBasp programmer to program an AT89S51. I don't know if this is a viable solution to the problem. It looks like one has to create an account to download the software to convert the USBasp to program the AT89S51. I have used an Arduino Mega as a programmer to program eeproms (28C256) on a breadboard. That would be a way to parallel program the chip, which takes a lot of bus lines.