Looking on the internet deeply has found these results:

a request for is the most popular phrase on the web.

a request of 130,800,000 results on the web	a request for 183,100,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
It doesn't look like this phrase is very popular! The search could not find any examples on the internet.	The message is a request for information. By letter of 13 May 2005, Cyprus submitted a request for recognition of Morocco. The Member States concerned should cooperate in assessing a request for authorisation of a clinical trial. I saw a request for proficiency evaluations for all CTU personnel on my secondary screen. Statistical data followed by a request for a reply. out. Before making a request for the initiation of criminal investigations, Europol shall inform Eurojust accordingly. If you hear muffled screams, consider that a request for a beam

a request of

130,800,000 results on the web

a request for

183,100,000 results on the web

More popular!

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

The message is a request for information.
By letter of 13 May 2005, Cyprus submitted a request for recognition of Morocco.
The Member States concerned should cooperate in assessing a request for authorisation of a clinical trial.
I saw a request for proficiency evaluations for all CTU personnel on my secondary screen.
Statistical data followed by a request for a reply.
out.
Before making a request for the initiation of criminal investigations, Europol shall inform Eurojust accordingly.
If you hear muffled screams, consider that a request for a beam