I have found and ordered a copy of F. L. Griffith The Nubian Texts of the Christian Period (1913), which apparently has some 130 pages and contains all texts known at that time. It includes the Miracle of Saint Menas, one of the longest available texts in this language. This text was contained in a manuscript which was purchased by the British Museum in 1908. According to the description by E. A. Wallis Budge, it measures about 15.5 by 110 cm and consists of 8 leaves of parchment in three quires, and is bound in covers of brown leather. This book is out of copyright in the US, so I will see what can be scanned from it.
Postscript. According to Copac, F. L. (Francis Llewellyn) Griffith lived from 1862-1934. The latter is more than 70 years ago, so puts all his books out of copyright in Britain and the EU, as well as in the US.