Lucan County (N4 beside the Spa Hotel) has it on Draught, at only €3.35 a pint!
They also had O'Hara's Red on tap (€2.85 a pint!) but Red Ale is a hard sell in Ireland, and I guess it wasn't selling. They replaced the Red with Fosters of all things.
They also have Galway Hooker on tap.
(edit: not city centre but good things are worth making the effort for!)