Firstly, There is no specific Du`a for having a good job. A Muslim always prays to Allah to grant him what is good in this world and in the afterlife.
In order to get what is good, a Muslim should always make use of Du`a and try to choose the best words when making Du`a, for Du`a is an unfailing weapon indeed.
Secondly, a Muslim seeking for something good may say: “O Allah facilitate all good things for me wherever they are and drive all good things to me from everywhere.” Another good Du`a is: “Our Lord! Grant us good in this world and good in the next and save us from the torment of the Fire.” (Baqarah 2: 201)
He may also try this Du`a: “O Allah! Grant me lawful sustenance which is abundant and blessed.”
Another thing we are to direct People’s attention to is the fact that one who occupies himself with praising Allah, while exerting efforts, is really helped. In the Hadith Qudsi, Almighty Allah declares: “He who occupies himself with remembering Me that he asks Me not for his needs, I give him better than that which I give to those who always ask.”
Dr. Monzer Kahf, Scholar in Islamic Economics and Financial Expert said,
“There are the du’a that we say during the sitting between the two Sujuds, it has “wa Rzuqni” (give me sustenance) and the famous Duaa of seeking protection of Allah from depression and sorrow, incapacity and laziness, etc..”
Lastly in addition to making du`aa’, one should spare no efforts to find a good job. He may seek the help of good Muslim friends or/and the imam of the nearby Islamic center.