Siobhan, try some of the Celtic Fests near you. I find most fests now have music dealers and have always found ETH in the selections. ETH sells two of their own cd's at their shows, Casualties of Retail and ETH Live. Those are the ones that I find that the vendors are selling, even though there are four cd's on the ETH page
https://nt7.magma.ca/indiepool/sc.asp?n=15575 . If you buy them off the ETH page, the shipping from Canada could be expensive.
Any cd shop should be able to order them for you. Make sure you ask the price for a special order. Some shops may tend to rake you on that.