How about you learn to make your own?
Cheaper by far in the long run.
Simply use whatever amendments you prefer to make your specific SS...You then take this nutrient mix and add a specific amount to your soil build.
"Cheating" can be done by simply adding less to prebuilt soils in a variation of what
@Richard Drysift says...
Here is where I would give you a link to explain building water only soils for beginners. Thing is, I got a new PC and lost all my links in a crash...
Hang on, I'll dig this one up again..
https://forum.grasscity.com/threads/easy-organic-soil-mix-for-beginners.1116550/
If you still want to pay for a product to simply add to soil? They even have their own prebuilt soil.
Take the time to look at this one. These guys are about the best out there! This is the page that gives you the info on doing what your wanting to do, and why to do it that way. it clears up misconceptions and tells you why some things are NOT good to use - organic or not....
https://buildasoil.com/pages/the-complete-system
Now then. Here is another link to a thread that really expands on what Richard has said. She goes about it rather differently but they work for the most part.
I must say I don't agree with all her formula's and what she use's....not to mention her concentrations but, It is a starting point and is pretty good for the beginner,looking to water only run.
https://forum.grasscity.com/threads/soil-mixes-no-nutes-water-only-post-them.611419/
Good luck