I'm trying to activate the 'reference product review records' suitebundle ID 53053, but it's not in the list of extensions in the activation wizard. I've reinstalled the bundle and there are no errors... Any ideas on how to get that to show up?

It’s not an extension. You have to rerun the field set script.

I only see a user event script, it looks like it sets the verified purchase flag. I can manually add those fields to the field sets, is that all that's needed?

Please follow the steps in the documentation, https://netsuite.custhelp.com/app/answers/detail/a_id/35030