You could use an ATmega88, ATmega168 or ATmega328 instead of the ATmega8, but will need to re-compile the firmware for the new microcontroller from source. The FabPDI-mega8 programmer is based on a modified USBasp for PDI programming.
FabPDI-mega8 | FabPDI FabPDI DIY ISP/PDI programmer that can be fabricated in a Fablab View on GitHub FabPDI-mega8