hazardeusDescription says the Auteur and Ori pads fit the HE series. You may need to buy the plastic ear cup rings from Hifiman or canabalize the ones glued to the OEM pads.
mattrisThe Oris are probably the only ones that fit though. There are very few pads that fit the HE-400I/4XX, and Head-Fi seems to love to put Ori pads on HE-400Is and other Hifiman headphones.