I find the Lawton Audio Denon leather pads to provide the greatest comfort. They also fit the HE-6's dimension perfectly. However, not everyone thinks they affect the SQ positively (I do). To keep the closest sound to the one you have presently, your best best would be the Beyerdynamic velour pads. They are slightly smaller than HiFiMAN and require more work to get the plastic rings inside the lip on the back, but it can be done.
JMoney is also selling the last leather Beyerdynamic pads for charity, at 50% off. It's the last occasion to purchase a pair before they're discontinued.
I encourage you to get a set of leather and a set of velour pads and see which you prefer.
From reading the thread, I believe JMoney hopes to return with future offerings at some point, but with lower costs. I'd like to see that option happen. But, also, we have many more sources today than just two years earlier. At that time, JMoney had a great operation running since there were not a lot of other suppliers in the market.
I'm wondering if we could see if Jin (Headphonelounge.com) might offer some pad options for the HifiMAN. He's in Singapore, but sells a lot of Grado leather headbands and has now come out with leather covers for the Grado foam ear pads for $40.00.