Sentinel-3 L1B to L2 NRT processing

I need the NRT processed Sentinel-3 OLCI data for an Ocean Colour application, however, this data seems to be removed once the NTC data is processed. The issue is the algorithm I am using is optimized for the NRT data and running on NTC data provides a lot of errors in Chl-a prediction. Is there a way to process L1B data into the NRT product myself? What are the main differences between the processing of NRT and NTC data – the main differences are in bands Oa01-Oa06.