You can obtain data for an OLR index here (scroll to the very bottom):

http://www.cpc.ncep.noaa.gov/data/indices/

It is for the region averaged between 160W-160E on the equator.  However, we find that the region 170E-140W tends to be better related to ENSO, but this index is not yet available.  We plan to eventually show it on the new CPC webpage, which you can preview here:

http://www.cpcpara.ncep.noaa.gov

Click the ENSO tab.  Hopefully the new OLR indices will be rolled out on the new webpage in the next couple of months.