Chlorine for water purification is also called sodium hypochlorite. It is widely available. Amazon has it in many different forms. Go here for more information : https://www.cdc <DOT> gov/safewater/chlorination-faq.html
I also suggest you put some references in your kit.
The Ranger Handbook, https://archive <DOT> org/search.php?query=Ranger%20Handbook (Take your pick, they are all there.
FM 5-34, Engineer Field Data, https://archive <DOT> org/details/FM5-35/page/n1
FM 21-10, Field Sanitation, https://archive <DOT> org/details/FM21-10_2000/page/n0
Each of these has different data, including how much sodium hypochlorite to use for water sterilization. Something like 1 canteen cup for a water buffalo. How to build stuff. How to stay healthy. The 'obsolete' versions are pretty good too. They are based on muscle power, not machines. You get the idea.
SOP's, maps and route plans / strip maps, pioneer and engineer tools / gardening and carpentry tools.
My father was a Combat Engineer in the early 1950's. When he decided to renovate the house in the 1990's, he asked me for a copy of FM 5-34. It's that useful.