Soil Blockers

Hi All,
I’m looking for advice on soil blockers.
No.2 Daughter bought me a soil blocker for Christmas and whilst there seem to be a number of “recipes” for the compost needed to use it, I have struggled to get all the necessary components.
Is anyone aware of a proprietary compost that I could use in place of these specialist mixes?

https://www.soilblockers.co.uk/

T63