Falcon is not a product, but rather the name we use for the latest platform module installer, and so you will not see it available in your custom portal. What you should see available for download is the latest version of the products you own for the period you were covered by active maintenance.
When logged into the portal, navigate to Downloads -> Download Product. NPM 12.5 is available both as an online and offline install which is using the falcon installer. The workflow is identical in both cases and will allow you to choose any additional products you would like to evaluate.
As a bonus, users who are running platform 2019.2 modules such as NPM 12.5 or later will benefit from Perform a centralized upgrade of the primary Orion server and all scalability engines