Dear Dr. Sravana Borkataky-Varma,
I believe that the construction of maps for the period prior to the Gushri Khan's consolidation of Central Tibetan power in 1642 would be hazardous - the fact is that the whole Tibetan region was a patchwork of local
regimes whose territorial limits are not well understood. After 1642 mapping can be by no means exact (for instance, the Fifth Dalai Lama's government was pretending that it had authority in regions such as Baltistan, in which Central Tibetan governments had
not exercised power since the 9th century).
Some years ago Wisdom Publications, I believe, used a range of maps from the 19th c. on to illustrate its annual calendar - you may wish to check with them to see if that is still available.
good luck,
Lecturer
Department of Philosophy and Religion
University of North Carolina Wilmington
Co-Chair, American Academy of Religion, Yoga in Theory and Practice
https://rice.academia.edu/SravanaBorkatakyVarma