The Portsmouth winger, who is eligible to feature against the non-league side at Broadfield Stadium, will now remain with the Robins until January 4.
The news will come as a big boost to manager Danny Wilson with Ritchie having excelled during his second loan stint in Wiltshire, scoring twice in 11 appearances.
Fellow loanee David Ball will not be available for the cup clash against Crawley having not been cleared by Manchester City to play in the 4-0 win at Plymouth in the first round.
Midfielder Jonathan Douglas is doubtful having been forced off with a groin injury in the 1-0 league defeat at Notts County in midweek, although Simon Ferry could be a straight swap having returned from his ankle injury to make the bench.
Kevin Amankwaah (knee) and Vincent Pericard (groin) both trained on Thursday but the encounter could come too soon for them.
Source: PA
Source: PA