stochstar
check the following link which provides daily shorts opened.
Note it doesn't provide an accummulate total, so you don't know what has been closed. but it is enough to give you a feel.
https://www.asxonline.com/intradoc-cgi/idcplg?IdcService=ASX_COLLECTION_DISPLAY&hasCollectionID=true&dCollectionID=68&SortField=dInDate&SortOrder=Desc