I figured this out. Its not actually a confluence function.
on the Jira dashboard page where you create wallboards/dashboards and other gadget type things you can grab the gadget url, its available in the add new item selector menu's.
In Confluence you have to go to General admin/External gadgets section. Copy the URL from the Jira dashboard gadget and paste it into the add a new gadget section.
it should now be addable via the macro button in confluence.
As a side note I also integrated Jira/confluence so that the auth would Passover. I'm not sure off the top of my head if this was a required step. I'm following this thread if you need additional assistance.
I have to agree with d7766903362f I can't find it, not even on the Atlassian Marketplace for Confluence. Is this Gadget restricted to specific regions?