I saw some really cute stuff in a Garden Centre on the back road in Ratoath (known locally as the Cottage, I think)...depends on how much you'd like to spend. It wasn't that expensive, but you can probably get cheaper in one of the big chain DIY stores, or even Smyths or one of them...
You can also get loads of grow-your-own kid friendly flowers and vegetables which look like other creatures - fun stuff, and they love to watch the progress (or, so I'm told!)