See here Note prices are in stg. Strangely enough can't find this in the current Irish catalogue but that does not say that its not available. You could check it out on the ring and reserve - 01-2161616.
BTW good choice of car - Mazda. The 626s are very comfortable for families and sturdy also.
I bought a roof box from OMearas camping, a big long one for a ford focus estate. It was not a huge price but quite flimsey, you need to mind it but is ts the dogs. Great for a w/e when we bring the kids and the dog. If u plan on using it a lot, consider getting one of the more rigid waterproof (our one does let some water in, just enough to do a bit of damage).
I seem to remember from a previous discussion you are going to France - If you can hold out buy your roof box and bars over there. We bought last year - I will check with the other half for exact details on this but I know they are considerably cheaper than the Irish suppliers and are widely available - most of the major shopping centres will also have some sort of auto shop (for the bars). The supermarkets sell roof boxes also but the better make of boxes can be got in the auto shops.