OpenBRF is a valid alternative, was not aware that so many are still useing the old brf editor ^^
At the item entry in module_items.py you can make use of the ixmesh setting
ixmesh_carry, you can see this being used at swords for scabbards or at munition like arrows, bolts, etc. So you can copy paste your item in OpenBRF (or BRF Editor) and add it in the item entry as follows (example taken from Native):
Code:
["hand_axe", "Hand Axe", [("hatchet",0), ("hatchet_carry",ixmesh_carry)], itp_type_one_handed_wpn|itp_merchandise| itp_primary|itp_secondary|itp_bonus_against_shield|itp_wooden_parry, itc_scimitar|itcf_carry_axe_left_hip,
24 , weight(2)|difficulty(7)|spd_rtng(95) | weapon_length(75)|swing_damage(27 , cut) | thrust_damage(0 , pierce),imodbits_axe ],
The rest is about trial and error. Try with the different available carry flags. For the right hip you have: itcf_carry_dagger_front_right, itcf_carry_quiver_front_right, itcf_carry_quiver_back_right, itcf_carry_quiver_right_vertical, itcf_carry_revolver_right.
First test which carry flags looks the closest to what you want to look it like in-game. Afterwards rotate the mesh in one of the above mentioned editors until it looks alright, testing it in-game.