What is the ruling on purchasing in installments from Jarir Bookstore at the cash price if the banks supporting the service are usurious and the product is not available elsewhere?

The type of support provided by commercial banks determines the ruling on the transaction. If it requires opening an account or obtaining a credit card from an interest-based bank, it is impermissible, because dealing with interest-based banks is forbidden when an Islamic alternative exists. If the item is only available in that bookstore, it can be purchased without entering into a forbidden transaction. One can borrow the price or engage in a Tawarruq transaction with Islamic financial institutions.