The Reading striker, 19 , who also had a loan spell at Roots Hall last term, has scored four times in 14 appearances for Tilson's side.
"Hal's agreed to stay for another four weeks which is good news," Tilson said.
"He's naturally left footed and provides width and competition on that side of the pitch.
"That showed when he came on against Crewe and he almost scored with his first touch."