Then you should offer to pay them for one. I’m sure they’d love to hear from you, and they could probably deliver one to you for the right price. But it will be a high price.
I feel like you aren't really understanding what a Service-level Agreement actually is in practice. It's not a piece of paper with a specific number of nines and an associated price tag. They can be and often are very complicated documents that take multiple rounds of redlining to arrive at something both parties agree to.
If zero data-retention was non-negotiable for the customer, it's totally possible that the negotiations ended there.
I'm not sure what you're trying to accomplish or unearth beyond what's already been said, which certainly suffices for me.
As both an attorney and SRE, I understand what an SLA is. And you can absolutely get an SLA when you buy cloud services from many vendors, including AWS. Some vendors provide it at all price points; others include it at higher service tiers, without complex negotiations needed at all. And, yes, if it’s not on the menu, you may need to negotiate one. But you can’t conclusively say “they don’t offer one” unless you’ve actually gone to the company and asked.
[0] https://code.claude.com/docs/en/zero-data-retention