You don’t need to. Go to the grocery store or wherever, and buy an itunes gift card and use that. When you go to redeem it itunes will try to cajole you into giving them a credit card number, too, but you can just skip that part.
I am not sure what you mean when you say it won't compete with La Boheme. The Pilgrim's Progress is a beauty, with snippets from many of Vaughan Williams better known works. To my way of thinking, he had a way with harp.