According to the experts there are only two or three companies that can produce moulds for the Ety's.
I went to my local ear doctor, got some moulds made and they worked well - for a while. Problem now is that the headphones just won't stay in the moulds. I'm getting them re-made but it's beginning to look like they're right - hopefully I will have some success next time round.
Mine cost £50 but I think you're probably looking at $100 or thereabouts.
One useful hint - when you have the impressions for the moulds made, make sure you move your head around, make chewing movements with your jaw, hold your head up and open your mouth wide to ensure you get a good fit. Make sure they take a deep impression too.
I hope this helps.