Dear Sharon: thank you for your email to Ireland Reaching Out and welcome to the site.
It sounds as if you have checked the civil records on the. Irish Genealogy website but it might be worth checking again. In addition, church records for some of the Dublin parishes on the Church records section of the Irish Genealogy site which you should check. Further to that, some of the Dublin parish registers on the National Library website have baptisms recorded online up to 1917. These should all be checked.
You can also add your grandfather to the ancestor database on the XO Chronicles (located at the top of the page). If you need any further assistance or have any questions, please feel free to email me at: firstname.lastname@example.org.
Good luck with your research!