Can anyone help me obtain invisible powder that will indelibly stain the hands of a thief in the workplace?

I believe that this powder, picked up by the thief without realising at the time that the item he is stealing has been treated, stains his hands bright blue and the stain cannot be removed for some time. I cannot afford to set up surveillance cameras so this seems to be the sensible way of approaching an awful problem, if only I knew where to obtain the powder. Any ideas? Please!