gen_im_npc_ammo_quiver_qunc.uti
is the cosmetic spears on back 'quiver' from screenshots above
gen_im_npc_wep_two_qune.uti
is a spear from the above quiver in the hand.
If you open up the _two_qune.uti with tlkedit you can see it has a special projectile override setting that makes you fire 'spears'.
The baseitem INT determines what animation plays, the default (1001) is two handed weapon but if you change it to bows (1101), it will now mount on the left shoulder, carry in your left hand and you will draw it like a bow, firing spears at your target. Baseitem staff (1200), one handed sword (1,000)...
I do not know the spear basetype INT. If it exists its all you'll need because you can define damage type/restrictions etc with properties cribbed from any bow.
It looks damn weird firing giant spears from a spear drawn like a bow.