SQL Server IO per session Activity Monitor can show real time the overall IO performance in MBytes/s on a server, but cannot show the same per session level.

I know about DMVs, and sp_who2 to retrieve session level io consumption , but there, its only the number of reads/writes can be extracted, not the actual Megabytes/s.

How can I see real time, session level io performance in MBytes/s?
You can use either a Profiler trace or sp_whoisactive to get the number of reads per session.  Reads are the number of logical disk reads in 8KB pages, so if the number of reads is 2, for example, that might equate to 16KB of disk I/O.