Hello Soumendu Sinha ,

I know ST Microelectronics here close to Grenoble (Crolles R&D) have been working on FD-SOI for a while. They would be my first suggestion.

https://www.st.com/content/st_com/en/about/innovation---technology/FD-SOI.html

You could also check Global Foundries, I believe they are now working on 12 nm technology:

https://www.globalfoundries.com/technology-solutions/cmos/fdx/22fdx

My other suggestion would be to look at the relevant wafer producers and ask if they know of any small companies producing FD-SOI MOSFETs for R&D.