The texture path is defined seperate from the mesh path in the item definition.
<GameItemTypeModel>
<ModelFile>gfx/hkb/Weapons/K_Club_01.hkb</ModelFile>
<Texture_All>K_Weapons_Basic_Texture_01.png</Texture_All>
<Attachment>hand_right_Lcf</Attachment>
</GameItemTypeModel>
just change the filepath. Although I think it has to be withing the "GFX" folder.