Sorry, I read your question incorrectly. I thought you were asking about resources you could recommend to a client who has vertigo, versus resources for training a client with the condition.
The client I’m currently working with who has vertigo is in a small group personal training situation on a pilates reformer. When I know she’ll be in class, I do more smooth transitions from machine positions, so we’re not standing up, lying down, standing up, lying down. Also, I’ve spent time with her individually, showing all of the modifications she can do to movements that don’t feel right (for her, head below heart is a no-no). She also knows that when I cue movements, I don’t expect her to transition as quickly everyone else, and not to be pressured to move quickly when I cue the next move so that I can keep the class running at a normal pace. That takes discipline on her part, moving at the pace that works for her.