I bought two for my dogs to try out and they like them, but now i cannot remember where i got them from. I like my dogs to have them as they are not as fatty as pigs ears.
Try Zooplus, they have most chews, if they don't have lamb ears they do have rabbit ears which I would think would be on a par with lamb on the fat front.
I had a look on zooplus Celli but they don't sell sheeps ears which is a shame, and rabbit ears a feedback said they are greasy so that's no good. But thanks anyway. :)