I am trying to find some information about the Kingdom of Raja Dahir of Sindh. For example, how much area did his empire constitute and where was it generally located? If anyone could also provide a map that might indicate some of this information, that would be particularly helpful.
As the Wikipedia article itself says, King Dahir was the ruler of the Sindh, and some areas of Punjab, the territories that now lie in Pakistan.His capital was at Alor, which is now in Sind province of Pakistan. There are no maps showing the kingdom's borders, since they are not completely known till now.
Just from researching the subject on Internet it is easy to see that the subject is very much charged with nationalist and politic agendas. Also if some detailed maps existed, exactly for the reign of Dahir they could not be undisputed, since there are obviously no scientific measures at that dates, also most of the historic references of Dahir are related to the Arab conquest and Dahir's defeat:
For example this book is saying:
During the reign of the Umayyad caliph Mu'awiyah I (661-80) the Arabs launched a successful series of offensives against Sindh, Al-Hajjaj, the governor of Iraq, appointed Muhammad Kasim as the commander of his armies in Sindh and made elaborate arrangements to ensure the success of the campaign. Al-Hajjaj ordered 6,000 Syrian warriors to join Muhammad's forces. After further preparation, Muhammad advanced into Sindh and toward De-bal, the capital of the Hindu ruler Dahir, which he captured after a brief struggle. He then moved on to the banks of the Indus, where Dahir confronted him on the opposite bank in 712.
Here you can find a map regarding that conquest in that timespan.
Same book as the link above:
From their newly established bridgehead, an Arab army, led by Muhammad bin Qasim, the governor of Iraq's son-in-law, launched attacks against Sind in 712, and Multan in 713, both of which were successful. King Dahir of Sind, a poor ruler who was already experiencing internal administrative troubles, was unable to defend his realm against the Arab onslaught; he perished in battle and his kingdom was absorbed by die Arabs.
I am sure you can find more if you research a real library. For example for Europe I saw atlases from a lot of periods, and and amazed at how often borders change in relatively few years after the fall of empires also in this case probably the fall of Gupta Empire.
Only this much I could help.