Good day,
It depends on how extensive a captive portal you need. Here is what we have available today:
https://documentation.meraki.com/Go/Meraki_Go_-_Landing_Pages
These landing pages can be configured within the app, or you can point to an external captive portal of your choice. You should have a 30 day return policy available if you wanted to give it a test run.
Let us know what you think about this solution and if it covers your needs adequately.