Anyone know how to make a report outside of a game ending screen?

I would like to report a player who admitted to account sharing(specifically, he swapped his HON account for another guy's LoL account and was playing ranked on the new account).

I checked him real fast while in queue and he was 3 / 75 / 64 in his last 13 games and woefully bad in all of them but with a gold 4 MMR... he claimed this was his 12th game ever and so i dodged and lost my promo rather than waste 30 minutes playing 4v6.

I just wanted to know how I can pass on his name to riot since I can't seem to find a report player button outside of the end of game screen.