Not a complete answer, but something to help you in the right direction.
As far as Europe are concerned, developing products based on operational meteorological satellites is the responsibility of the EUMETSAT Satellite Application Facilities (SAFs). Some of them work on clouds, for example, the group at SMHI in Norrköping, Sweden. However, as far as data are publicly available at all, cloud masks are not available near real time.
The main users of a near real time cloud mask would be operational weather forecasting people (Numerical Weather Prediction (NWP) SAF or Nowcasting (NWC) SAF). They are not known to offer raw data such as cloud masks near real time for free, though.
Of course, you could "simply" build your own satellite receiver, download AVHRR FRAC data directly from the NOAA and MetOp satellites, and operate your own algorithms to extract clouds. You'll need some pretty powerful hardware to do so, though. Which just might explain why near real time open data may be hard to come by.