Using a user's password as an API parameter

I have an app that uses a 3rd party API call for an account that the user already has with that 3rd party. They are able to retrieve their API key for that service by entering their username and password for that service.

Instead of saving any of these credentials to the database, I make the user retrieve that API key every time by asking them to sign in every time and then I just hold that API key in a state while they’re browsing that session. Of course, this is ridiculous, however, it does allow all of their secure info to be secret, even to me as the developer.

However, the UX here is not sustainable and it would be nice for the user to create a Bubble accout in my app using those same logins, but again, no one would have access because we never see a users’ passwords when they sign up to a Bubble-created app. This way, only their email address could at least be saved to the DB as a User and they could opt for “Remember me” to save them typing in their username and password every time.

Theoretically then, I would like to call the 3rd party API by using:
username: Current user’s email
password: Current user’s password

However, “Current user’s password” is not an option in Bubble.

Any ideas?