Download UMDGen v.4.00 and load up the ISO in it.
Open up the PSP_GAME folder and the USRDIR folder in it. The fftpack.bin file should be there. Right click on it, select "Extract selected...", and save it somewhere.
Open up the PSP_GAME folder and the USRDIR folder in it. The fftpack.bin file should be there. Right click on it, select "Extract selected...", and save it somewhere.