Office definitely do them and schuh do some as well. If you want to save yourself the €5 delivery charge just call up the store tell them what you want and they won't charge delivery. I never understood why but this is how I do it they end up coming from the same place too.
Amazon are however one of your best options if you know the size.
Online will be your best option then. The good news is sizes don't differ between colours / styles and if the child is size 2 in general then size 2 in converse will be perfect.
Converse are now owned by Nike, so it is more difficult for the smaller childrens clothes shops to get small amounts of stock.
Little Piggy's shoes for kids in Naas is listed on as a stockist as are Champion sports