unfortunately, pads are starting to cost a really silly amount for what goes into them.
You could sell them and buy a new unit. As mentioned the K612 is going for around $150 now, which is a pretty good price. Also you could get a Q701 for about $180 new, or sometimes amazon has "open box" returns which usually are in very good condition. Sometimes people get brand new headphones with a damaged box. Those usually run in the $130-$150 range.