How to monitor Darkweb if credentials of our SaaS product are leaked?

We operate a Software as a Service (SAAS) product. Recently, we were notified by an online security provider that a user's credentials from our platform were exposed on the Dark Web. How can we proactively monitor the Dark Web for such incidents? Are there any subscription-based services available that offer continuous monitoring for this purpose?

credentials cybersecurity dark dark web darkweb exposed incidents leaked monitor online security platform product saas security service services software software as a service subscription web