"It's disappointing news," admitted Alexander, who is now hoping to sign a Championship striker on loan ahead of their weekend visit to Aldershot.
Elliot, who has represented England at U-18 level, caught Alexander's attention playing for Leeds' reserve side.
Alexander added: "Having seen Tom play a few times for Leeds' reserve team he would have been a very useful acquisition for us. But having picked up the injury, coupled with doubt as to its severity, it wasn't right to continue at this stage."