There is unfortunately no such functionality OOTB  It is only in on premise Nintex.

The only workaround I have in my mind is to not send reminders using "Assign a Task" action, but to create a parallel block action:

1. In the first branch add assign a task (with "Reminders" option unchecked) 
2. In the second branch add a loop with pause for duration action, because in "Pause" action you can set that the pause is only counted for business hours:
   
   
   together with and "Send email" action that will in fact send your reminders.

Be aware as well to set up "Completion Condition" in "Parallel Block" action, so that once your tasks are approved or disapproved your second branch will be ended. In the end the workaround would look like this:

Regards,

Tomasz

Hi Anne,

         You can try using a Nintex Site Workflow and schedule it to run accordingly .

Regards

 Bashya Rajan A

Please, read carefully. This is not Nintex on premise, but online. There is no such feature as scheduling for site workflows.

Regards,

Tomasz

Thank you, Tomasz, we'll give this a try.  And thank you for including a screen shot, the visual is very helpful.