There should be a link from the game page, but the poorly designed NHL website makes it hard to access. For each game, select Ice Tracker rather than RECAP at the bottom of the page. Then select 'BOX', and scroll that left side of the page all the way down to 'Official Game Reports'.
The URL formula is
sprintf('h' + 'ttps://www.nhl.com/scores/htmlreports/%d%d/PL%02d%04d.HTM', season, season+1, stage, season_game_id);
Season game id runs from 1 to 1312 this season for regular part, and is a bit trickier for playoffs. There it's a 0ABC, where A is round (1-4), B is pairing of the round (1-8, 1-4, 1-2, or 1), C is the number of the game (1-7) The last game of the playoffs this year was 0415.