You can make your own if you're talented and you can send away for a pattern from Irish Threads. But the dropped waisted dresses in fashion now are hard to find patterns for.
Please Note: It is illegal and unforgiveable to copy someone else's dress. Even if your daughter says she wants a dress just like the one she saw on the web, explain to her that it is not allowed. There are many talented designers around, for a reasonable price you can have an original. Especially in the higher grades, a knock off will be noticed and your daughter may suffer because of it.
Materials to use are gabardine for beginners and Velvet/Gabardine or Thai silk or lame for the Open Grade Dancers. Some dresses use very thick stiffening to get that traditional look. And celtic embroidery designs can be purchased from America from the Irish Dancers' Catalogue. You might be able to find some local talent to help you with the designs, but the embroidery and applique is done before the dress is assembled. Always seek the advice of your teacher before you make costly investments. If you are too chicken to make your own.. try a professional. But be prepared to join a long queue, give as much lead time as you can. Irish Dancing Dress Makers in Australia