Dunnes store have had large bean-bags in the past "Fat Boy" was the brand name. Don't know if they still have them or if they only have them in some of the larger stores
Place by the entrance to tescos in paul street or another place across from the church in blackpool both make them up in whatever size you want. Think you can bring in your own material to both places if they dont have exactly what you want
Try Budda bags - they're miles better than bean bags, as they contain memory foam and really keep their shape when you're sitting in them - almost like a very comfy armchair!
They have an outlet in Dublin but can also be ordered online.
we got one a year ago and it's been used by practically everyone who comes into the house....