you have to make your own, buy the 11lb block, run tap (a lot) and hot water and break it in a 20gal bag or bigger while u clean it.
Then squeeze it run RO Phed 5.5 Calmag through it and let it saturate in a pan....yea it's a pain to prep but worth it. I run perlite and light organics with it too for a bit then i dont need to ph a lot if im near 6.