It appears Sennheiser no longer has customer service available after the company sold off the brand. They do not even respond to email. They may not provide anymore after sale service for their products. It's a shame and will upset many loyal customers. The OEM pads for this iconic headphone is no longer available and the only option is to go with third party manufacturers which will alter the performance of these headphones. If your original pads are worn out, there's no other option than to get used to a new sounding HD800 with third party ear pads such as the Dekoni.
These are such bad pads, avoid these if you cherish your HD800/S, Elite Hybrids are just bass killers that also mute the highs and overall ruin the soundstage, imaging, and just about everything. Oh, and they're hot as hell, so you may need a personal fan blowing at your face to offset things.