Hello mbernachi
Welcome to Microsoft Q&A Platform, thanks for posting your query here.
RedHat Enterprise Linux Server release 5.9 (Tikanga) is no longer supported by RedHat and is not available in Azure Marketplace.
Ref: https://access.redhat.com/articles/3078
https://access.redhat.com/support/policy/updates/errata
However, you can try this alternative of bringing your own Red Hat subscription to Azure and use it to create a virtual machine with Red Hat Enterprise Linux Server release 5.9 (Tikanga) and see if that works.
Ref: https://learn.microsoft.com/en-us/azure/virtual-machines/workloads/redhat/byos?tabs=AzureRM
Hope this helps.