Where can I find the Elfix polarity tester?

Trying to test polarity of the various gear in my setup. Having no success finding one of these. Any suggestions?
It used to be available at Audio Advisor, check with them, or buy the van den Hul version. Regards, Alan
Thanks guys; Audioadvisor has not carried this for a long time; I have the Van Den Hul and am not impressed with it.