Some services will take gift cards. You find out the amount you need to pay, and convert it to your currency, buy a gift card in cash for the amount, then send the code from the gift card to the service.
You have to trust that they won't just run off with the funds, but the whole point is to pick a service that you trust in the first place.
I don't remember the steps, but there used to be a way to do it through Calibre. You could download your library into the Kindle desktop program, run a DRM removal tool, and have them available through Calibre.
You might have had to remove the DRM through Calibre, I'm not sure. Hopefully this gives you somewhere to start though :)