I have some leather Beyer pads on my HE500. There is a small flap around the ring of the Beyer pads which you can put over the new Hifiman pad system with the 4 hooks that allows you to try different pads from other companies. I like it much better than the leather ones from Hifiman.
Do you know the exact replacement earpad model that fits the he500's? Or can you provide a link... there are like 30 different earpads to choose from on the beyerdynamic website!