API for secure data storage?

Have a payments problem we're trying to solve, would love HN input!

Our platform needs to make several payments to suppliers each week, the problem is we don't want to store our suppliers bank details. Unfortunately the only payment method possible right now is via a bank specific file (*.aba) and is manual, but to create that file we need to have stored our customers bank details...

Does anyone know of a platform which can store/retrieve customer sensitive data through an API so we can avoid storing it ourselves?