A. Use a Network Load Balancer (NLB) to pass through traffic on port 443 from the internet to port 443 on the instances.
B. Purchase an external certificate, and upload it to the AWS Certificate Manager (for use with the ELB) and to the instances. Have the ELB decrypt traffic, and route and re-encrypt with the same certificate.
C. Generate an internal self-signed certificate and apply it to the instances. Use AWS Certificate Manager to generate a new external certificate for the ELB. Have the ELB decrypt traffic, and route and re-encrypt with the internal certificate.
D. Upload a new external certificate to the load balancer. Have the ELB decrypt the traffic and forward it on port 80 to the instances.