SEPA Lastschrift is very safe, you can easily revoke any charge. So giving out your account number here is not a significant security risk. And otherwise credit

SEPA Lastschrift is very safe, you can easily revoke any charge. So giving out your account number here is not a significant security risk. And otherwise credit cards and Paypal are the main choices. You can probably just save your credit card information in your browser or something if that's the only thing preventing you from using the credit card.