Hey Josh,
Searching by metadata is definitely something we'd love to offer in the future alongside improved List APIs letting you provide a lot more criteria for you search. It's not something that we have a clear timeline for or that we're focusing on at the moment though.
For now, the best solution would be to mirror that information in your own database to let you search through it based on your own criteria. You can use webhooks [1] to ensure you keep your data up to date.
You can also search by metadata directly in the dashboard in case that helps. We have a support article that describes in details how our search works in the dashboard.
Hope this helps!
Remi