Don't know if this will be much help, but I was able to get excellent service from Sennheiser. I have the exact same headset. Best one I've ever owned. Super clarity, lightweight, low clamping force, very compact when folded. All around best and I've used most every brand. Bought it new at KOSH in 2010 and have put several thousand hours on it. Finally developed an intermittent connection in one of the wires. Contacted Sennheiser. They had me send it in, did a quick repair and sent it back for next to nothing. It has worked flawlessly since. Referenced the work order but it doesn't have a date on it. Ugh. That was approximately 6 or 7 years ago. At that time they told me they were no longer producing headsets for the aviation market. They were only continuing with their audiophile and recording industry business which was their primary business. I lamented how their product was the best, that they were ignoring a lucrative business, but it fell on deaf ears.
As I said, probably not much help other than, the company was still doing well in business just a few years ago and not selling aviation headsets. They were providing service however, and they indicated at the time that "some parts are still available" for the HMEC 460 series. Should you locate a source for those ear pads, I would appreciate knowing it as mine are beginning to show their age. I too will let you know if I hear of any viable options.
