I had a go at this the other day, but got a bit stuck after a while, due to difficulty in identifying parts from the sprite. The Combat Leather Jacket was visually the same as Leather Jacket in game - so the only reference image I've been able to find is the inventory one. I interpreted it as roughly the same as normal leather jacket, but with brown leather shoulders, a sort of cross over the middle, and some "stuff" on the arms.
But the brown stuff - is that fur, gecko skin, dirt, brown leather, extra pockets, a painted "tribal tattoo" like design?
Is the green stuff gecko skin, grenades, painted design?
Anyway, this is the model as is, put onto Karpov's body model (and with the skin texture and approximate boot shape taken from Ztormi's Leather Armour model)
In retrospect, it may make much more sense to just add extra parts to, or simply re-texture the existing leather jacket - assuming the model for this exists somewhere, but I fancied a go at it anyway, for the practice.