AWS load balancer and maintenance page

I'm using AWS Load Balancer with 3 EC2 servers, and I'm trying to serve a Maintenance page when site is under maintenance.

This page need to return 503 HTTP code, because it is a proper code for a maintenance mode and will prevent possible problems with SEO.

When I return 503 code from any of my servers, Load Balancer makes it "Not In Service", and when all servers return 503, website returns a blank page (because all servers are disconnected).

My questions are:

1) Is there any way to serve a static page from Load balancer if there is no healthy servers?

2) Or how to configure Load Balancer's Health Check that it will not consider 503 as a reason to mark server as "unhealthy"?

Thanks!