I just got a reply from HSV. They did get a HBD and a HSV plate but they didn't use the Sandman name. Here is the reply in red:

Hi Byron,

Yes, HBD did fit a few Maloos with canopies. They were never marketed as Sandmans though. As with all HBD product a build plate was fitted so HSV vehicles had two plates. This happened in many instances such as sunroofs etc.

Hope this helps.

Regards