Is there any needle-less tattoo gun Would be great so as to minimize the risk of virus transfer?
No there is no such thing. There would be no way to implant the ink into the skin without piercing the skin. Air brush?
Not quite right, it may not be in production but:
A patent (number 6,689,095) was issued in 2000 to Garitano; Gilbert (Alameda, CA), Garitano; Linda (Alameda, CA) The title was
"Methods and compositions for the needleless administration of permanent makeup and tattoos. In particular, the present invention relates to hypodermic injectors for use in delivering pigment or other desired substances to targeted layers of the skin, avoiding needlestick injuries and transmission of disease to the treated subject."