The Juniper software download page houses only images for VHD, QCOW2, and OVA types. An OCI image is not an available choice here.

There is not a direct image available for this particular format. As per documentation from https://www.juniper.net/documentation/us/en/software/vsrx/vsrx-consolidated-deployment-guide/temp-vsrx-consolidated-guides/security-vsrx-oracle-guide-pwp/topics/topic-map/security-vsrx-oci-deployment.html, it states that this needs to be created separately by downloading the vSRX image from our downloads page and uploading this into an OCI compartment:

NOTE: vSRX Virtual Firewall 3.0 image is not available in the OCI Marketplace. You must download the vSRX Virtual Firewall 3.0 software from Juniper Support Downloads and upload into an OCI compartment.

The same techdoc page will also direct you in how to accomplish this task as well.