The following publication is now available online and may be of interest to you:
An electronic book, The Toponymy of an Endangered Nubian Language by Dr. Abdel Halim SABBAR (2018), ISBN: 978-1-9998425-1-2, is now online for downloading from the United Nations Group of Experts on Geographical Names at the following link.
Or access UNGEGN Working Group on Exonyms > Home. Click on ‘Publications’. Download ‘The Toponymy of an Endangered Nubian Language’.