One of the most helpful and informative papers i have found on low cost TC is
this one. It has a table towards the end mentioning the full composition of the growing media(which is based on Murashige and Skooge basal salts recipe)of the convectional recipe and of one using more ordinary and supposedly easier to find materials. For you and me though,buying the salts ready from a shop like the one James suggested,is the easier and maybe even cheaper solution than finding all of the components and buying them separately. However,the low cost technics mentioned for doing the TC in this paper,are very helpful. Basically the most worrisome part are the sterilization and clean transfers to growing media which require some labor in advance,to prepare a clean area and a low pathogen count place to do the transfer,to achieve good results.
From my search on that so far,the easiest solution to that is making a glove box.