Registration token not available in the payload being sent from AJO -> ACC for real-time transactional message

Good day folks, I am trying to trigger a journey where the payload will be sent from AJO to ACC for real-time push notification for android and ios, my question is in the current setup, I don’t see any registration token field that can be sent into aec, I am wondering how to proceed, 

The registration token is present in campagin and linked to the userID, this userId is also sent over on the payload too, so can I script a lookup and match and send functionality and link it up with the template, I was unable to find an example on the docs

So what I want to achieve is that I want user the userID from the event and then use that to fetch the registration token from ACC and then trigger the push notification from the message template is this feasible, any relevant docs for the same?

Thanks in advance for the help