This response uses data provided by Google's Knowledge Graph It streaming: where to watch movie online?
The 2017 film It is available to buy online through major digital retailers including Amazon Prime Video , Apple TV , Fandango at Home , and Google Play Movies & TV . Digital Purchase and Rental Options
If you prefer a physical copy, many editions include a digital download code:
: Allows you to sync your purchase across multiple connected accounts. Physical Media with Digital Access