The RFL web-site lists 5 as the most drop goals in a match by one player...
Danny Wilson (Swinton) v Hunslet (John Player Special Trophy) - 6 November 1983
Peter Wood (Runcorn Highfield) v Batley (League) - 21 October 1984
Paul Bishop (Warrington) at Wigan (Premiership Trophy semi-final) - 11 May 1986
Lee Briers (Warrington Wolves) at Halifax Blue Sox (Super League) - 25 May 2002
I was at the last one.
Only 4 drop goals from 1 player (Johnnie Blair), but 5 in the game for Fax when they beat Wakefield 7-3 in the 1980 Challenge Cup Quarter Final. There were 6 drop goals in total in the game, with 1 each for Jimmy Birts and David Topliss as well. In those days, we could muster nearly 13k fans between us to come and watch.