'a written reply' is correct and usable in written English.
You can use it when referring to a response that has been composed and sent in writing, such as a letter or email. For example, "I received a written reply from the lawyer this morning."
The best way of getting the truth is a written reply from the minister.
In a written reply later yesterday, Mr. Dolan said he was "extremely disappointed" with ImClone's response.
In a written reply to the President, the Speaker said that the House had votes scheduled for six-thirty that evening.
"Yes, I would like to write one or two plays, when I am no longer president," he said in a written reply.
In a written reply, Smita Narula, an author of the report and a faculty director of the two groups behind it, said it "never claims that 200 people were entrapped".
Earlier this month, the Defense Ministry, in a written reply to the Parliament, said, "No irregularities in purchase of components of the Tatra trucks for army have been reported".
I put this complaint to former President Bush, who sent back a furious written reply.
In a short written reply to Cair on 17 April, the Justice Department confirmed that it has begun to monitor Morgan's gun range.
In fact, our complaints merely warranted a short written reply from the then chair, Sir Christopher Meyer, saying he was satisfied that no journalists were being put under any pressure to write inaccurate or unethical material.
In a parliamentary written reply to Mr Montgomery Hyde (C. Belfast N). the Home Secretary says that the Prison Commissioners' list contains six persons qualified to act as executioners or assistant executioners.
Bahmanzadeh sent a lengthy written reply the following day.
