I'm looking for free sources of radar (SAR)and optical satellite imagery of same scene captured at same duration of time (week /days/ month) but of same location.
Does anyone know of sources?
Check it out if you have not seen this the list you are looking for SAR.
The Vertex system is hosted by the Alaska Satellite Facility, and has an advanced search for Synthetic Aperture Radar:
Assuming you already got SAR data from somewhere. Maybe a different spacecraft acquired a similar view by flying over the same area immediately after the SAR data was gathered.
To find out, check out the NASA Worldview interactive viewer.
Worldview has powerful query- and downloading-features for hundreds of satellites, much of the data pretty recent. Still, often you can go back into the 1990s, and download the optical data for the scene you need. Maybe ask their helpdesk, dev team, or mailing list for your specific data needs.
Disclaimer: I've not done this. I only saw a talk at AGU General Assembly 2018 where a developer showcased the site.