I use PayPal's pseudo-Mastercard plug-in to pay for my Kindle purchases.
PayPal generates a valid MC number but takes the funds from whatever funding source you use with PayPal, say your bank account. This allows me to use PayPal with Amazon even though they don't accept PayPal directly. There is no additional fee for doing using this service.
https://www.paypal.com/us/cgi-bin/we...Plugin-outside
One of the other features of this plug-in is that you can generate 1 time use credit cards specific to that business so that you don't have to worry about someone gaining access to that credit card number, etc. etc. You can optionally generate a multi-use business specific number as well, as I have with my Kindle account, so that you can charge multiple times without having to generate new numbers every time.