Ask HN: How to get certificate of employment on a startup?

Hello, my family recently got a car loan in which I'm a co-author of it. Now after approval the bank is asking for a certificate of employment. Currently, I'm working at a startup where in we are still developing the app. We only have Mutual Trust that binds me and my co-founder.

How am I able to get or process a certification of employment if my employer is in the US while I'm in Asia?