Borax substitute is largely Sodium Sesquicarbonate and cannot be regarded as a substitute for Borax, which is Sodium Tetraborate.
Borax substitute is formulated mainly for cleaning tasks within the home and is not suitable for use on the skin. In fact, skin contact with Borax Substitute is more hazardous for the skin than contact with borax.
You can source Borax on ebay if you can't get it elsewhere as others have said.