Spark Coupon Subscription Without a Credit Card

I have a current Spark app where I'm finding that some people will want to be invoiced and pay by purchase order, rather than credit card. It's an education type app, and schools are more willing to pay by check than a credit card. So what I've been doing is putting them manually into Stripe, and then going into the database and manually creating the subscription information. It's doable, but not elegant.

Is there a way that I could use a Stripe Coupon instead, but without requiring a credit card? So, for instance, if a person buys 10 seats via an invoice, I would create a coupon for 100% off, set the max redemptions at 10, and create a random string for its name, and then send that to the user to distribute.

As far as I can tell, the Spark api requires a credit card to create a customer within Stripe. Is there a better way around this? Thanks!