I've had this for a few years, I use mostly a X300, its in excellent condition and works great, it's not "new", just so were on the same page. Below is an description from the internet and some pictures. $140 shipped PayPal.
Note: the batteries are in the unit.
Factory M2 Insight USP Tactical Light made specifically for the HK USP & USPC variants. This tactical light Fits ALL USP full size & compact models. No adapter needed ready to install. Comes with batteries and hard storage case.
Features of the HK USP/UPSC M2 UTL Insight Compact Military Flash Lights:
Penetrating power of 90+ lumens of white light
Lighter in weight than other models
Compact design is ideal for concealed carry
Integral on-off switch allows fingertip operation
Polymer body is chemical resistant
Standard 6-volt system
Attaches / detaches instantly
Optional remote switch available
Beam adjusts from spot to flood
Comes with 2 of the needed 123 battery
Limited Lifetime Warranty