create script for Stripe: assign a subscription to a customer who made a one-time purchase

I am building a Squarespace site, and need the ability to do recurring billing. I subscribe to Moonclerk, but that requires circumventing my Squarespace store (which I need for calculating shipping, etc, for physical orders). I have thought of creating Moonclerk buttons just for the recurring billing purchases, but that gets confusing for the customer. (They have to use one process to buy one-time items, but another to buy subscriptions, and the subscriptions won’t show in their purchase history in my store.) It occurred to me: is it possible to get the Stripe token for the credit card from a customer who made a one-time purchase (using the Squarespace store) and adding a subscription using that same payment method? This would solve my problem by allowing customers to "purchase" recurring billing items in my Squarespace store. They would actually be purchasing a "product" that cost the same as the first installment of the recurring billing plan. Then, I could manually invoke the script you will write, to create a subscription for that customer, based on the token for the payment method they used for purchasing the "product". Is this possible using the Stripe API? Can you create a script I can invoke for a given customer and a given Plan? I don't care how the script gets invoked! I can be through the Squarespace back end, through a webpage I would create elsewhere, through a desktop app (Mac only, please), or any other way you think is secure and effective.