Translation:Gurlak, they are looking for you.
Are you referring to "they" in the English translation? In actuality, the Klingon suffix -lu' is not passive voice, though it often translates well into the English passive voice. To put this sentence into the English passive voice you would have to do something like, "Gurlak, you are being looked for." That is an accepted variation. There is no direct way to translate this literally into English. Other, closer translations would be things like, "one is looking for you," "someone is looking for you," or "they are looking for you." In English it is not unusual to use "they" for some unspecified and unidentified individuals. In English people often respond with, "they who?" But you'll never get a response like that in Klingon because -lu' specifically means "I am unable or unwilling to specify and identify who".
You are being looked for and One is looking for you are both literal translations of the Klingon; I don't see why you say it can't be done.
On the other hand, They are looking for you is not an appropriate translation. In English there is nothing general or unspecified about using they here.
nInejtaH chaH They are looking for you.
Danejlu'taH You are being looked for; someone unspecified is looking for you.
In English there is nothing general or unspecified about using they here.
We may have to agree to disagree on this.
I agree with jdmcowan that "they" is commonly used in a non-specific manner in English, a bit like "you" in sentences such as "they say he's rich" and "you can't swim from America to China -- it's too far", where "they" and "you" do not refer to specific people.
I agree that the they in They say he's rich is an impersonal they, but the they in They're looking for you isn't. I think it only works as an impersonal they when it's part of a set phrase, like they say, or when they has as a postcedent a longer phrase, like They speak Klingon on Kronos (the they refers to people in general on Kronos; you couldn't just say They speak Klingon and expect the they to be interpreted as an impersonal they).