Check out Temporary Invoicing for Gum’s Med Fields. I believe Sammy is using PayPal invoices, so that could be an option for you.
Those sites are different from Gumroad, so what you had once been able to do on those sites doesn’t necessarily translate to the Gumroad shop. Even Soundweave had its Paypal issue. Plus things are changing. If you’d like some insight on this topic, you can read the Charge Back Black List thread.