you can buy Crystal Bright clarifier from Amazon https://www.amazon.in/gp/product/B07N57X13M/ref=as_li_tl?ie=UTF8&camp=3638&creative=24630&creativeASIN=B07N57X13M&linkCode=as2&tag=pritesh029-21&linkId=ff1b9e0e50026a8dd09eac3d4b563303 Or you can buy for your nearest Swimming pool Dealer.
This product easily available on Flipkart: https://www.flipkart.com/crystalbright-crystal-bright-pool-spa-clarifier-conditioner/p/itm929455c57a1b5?pid