Modify an Identity Pool Cognito JWT

I've joined a team working on an application that uses Cognito with Identity Pools and user state in Cognito Sync. We need to add some authentication to our process and the natural place would be to sprinkle a little data into the Cognito-generated JWT. I'd like to grab that data from, say, a lambda querying Aurora. I see that User Pools have a pretoken generation lambda trigger. Is there something similar I can do for identity pools?