What about something like this blog post (scroll down to "More complex example – NATing") (source code]), which would be a tiny application that can be deployed on EC2 in an ASG behind a GWLB, with the Source/Destination Check Disabled to allow people with potentially high egress costs to have a more resilient NAT instance infrastructure (and don't want to pay for managed NAT Gateways).
What about something like this blog post (scroll down to "More complex example – NATing") (source code]), which would be a tiny application that can be deployed on EC2 in an ASG behind a GWLB, with the Source/Destination Check Disabled to allow people with potentially high egress costs to have a more resilient NAT instance infrastructure (and don't want to pay for managed NAT Gateways).