On PFR, it has 20 sacks for the 04 Chargers. Philip Rivers was sacked once for 10 yards on 1/2/05 vs. the Chiefs, but it says 0 sacks on PFR. That would give the Chargers 21 sacks, and add 1 sack for 10 yards to Rivers' page. This is confirmed by nfl.com and the Charger's media guide.
Rivers nfl.com page -
http://www.nfl.com/players/philiprivers/profile?id=RIV651634
nfl.com page showing 21 sacks for 04 SD -
http://www.nfl.com/stats/categorystats?tabSeq=2&offensiveStatisticCategory=TEAM_PASSING&conference=ALL&role=TM&season=2004&seasonType=REG&d-447263-s=PASSING_NET_YARDS_GAME_AVG&d-447263-o=2&d-447263-n=1
The boxscore on PFR says 2 sacks for 17 yards. One of those was 7 yards on Flutie (which is correct on PFR), and the other is the 1 sack/10 yards on Rivers that needs added.
http://www.pro-football-reference.com/boxscores/200501020sdg.htm