Alternatives for enabling SSL on EC2

Solution 1:

Let's Encrypt

Let's Encrypt works with any host on the public internet, including AWS. I use Let's Encrypt on my AWS EC2 instance, and you've used LE on EC2 before. I'm confused why you think LE doesn't work with AWS.

I have a tutorial on EC2 / LE here. The version number of the software I use "ACME" is potentially an old version now, if you use that you should check for a new version.

Instance Size

If you need a larger instance, you can just stop your instance, change the size, and start it again. If you need a larger EBS volume you can expand the volume.

AWS Certificate Manager

This statement on the ECM FAQ is slightly confusing suggests you can't use public ACM certificates on EC2 instances.

Q: Can I use certificates on Amazon EC2 instances or on my own servers?

You can use private certificates issued with ACM Private CA with EC2 instances, containers, and on your own servers. At this time, public ACM certificates can be used only with specific AWS services. See With which AWS services can I use ACM certificates?

Conclusion

I suggest that you go back to using Let's Encrypt. If you need help please start another question saying what you're trying to achieve, what's not working, and show any relevant logs.

Solution 2:

This is going to seem like overkill but it works rather well. Set up a public facing application load balancer in front of the EC2 instance, and do HTTP->HTTPS SSL Termination with the Load Balancer. This will make it easy for you to swap out certs if you need to at the AWS level rather than the instance level. Update the DNS to point to the Load Balancer rather than the EC2 instance. There is a cost associated with this though, but it would probably solve the issue for sure.