Custom Access Denied Page for Office-365

Hi,

We provided custom access denied page for current on-premise SharePoint site using SPWebApplication.UpdateMappedPage method. The custom access denied page is there in _layout folderin current farm. Now we are migrating to Office-365, I would like to know how we can provide the same functionality in office 365. What is the alternate solution for this in office 365?

Thanks,

Pat