I don't think you're going to find it. The main vendors are hostile to this workflow. I get why, any flow that can exist to export passkeys can be used by hostile actors to walk a 75-year old millionaire grandma through handing over $$$. I think however that that's just a risk we have to make the bank and brokerages accept. It's not a problem with a technical solution.

Why is it more important than protecting users? They've already added a way to share them securely.

Wasn't the discussion you responded to about how they currently can't be shared and that the vendors don't want them to be shared as it breaks their desired lock-in?

They can be shared just not insecurely. That's why they are working on a spec.