Nolans Crabmeat is in Superquinn and some of the Dunnes do it. It is usually over where the smoked salmon, etc is. It is usually €9.99 for 200gms, I think and sometimes they have them on special. It is expensive enough, but beats the tinned stuff hands down. I make a crab and chilli linguine pasta dish and always use this and the quality of it is excellent.
Superquinn in Lucan do it, thats where I get mine and have picked it up in Dunnes in Clondalkin, though they dont always have it in stock.