Another ways to get PE
Can I buy PE in other ways?
Unfortunately there is only one way atm. and that is by purchasing it using amazon pay. If that doesn't work for you, which it sounds like, then you might want to contact the developer and ask to see if another way is possible.
You can find his email and twitter on the about page.
The Humble Widget is now updated to also support card and bitcoin payments, hopefully one of them will work for you.