How to get Horizontal Infrared Radiation Intensity or Opaque Sky Cover?

I am trying to create my own EPW file for the first half of 2021.

I have all variables except for Horizontal Infrared Radiation Intensity or Opaque Sky Cover (I need at least one to complete my file).

Is there any method I can use to derive either variable? Or is there a satellite, bureau of meteorology database etc anyone is aware of that I could source this data from?

Thank you for any help you can provide.

Horizontal Infrared Radiation is equivalent to 'surface thermal radiation' value available for all NWP models. If you need to look this up quickly, feel free to check out http://weatherdownloader.oikolab.com/ (disclaimer - I run this tool), based on ERA5 data from ECMWF. This should fit well under the free tier and you can download up to 6 months of data without signing up.

The parameters are named 'surface_thermal_radiation' and 'total_cloud_cover' (for the opaque sky cover).