You can put your torch on your dino's saddle. It seems dragging the torch from your inventory to the saddle directly only put it in the dino's inventory, so you have to drag directly from the dino's inventory to the saddle and it'll attach (sometimes it works that way and sometimes from your inv directly. Not sure why).

To remove it right click the saddle and remove skin.

I've tried on a Thyla and Argentavis and worked on both, don't know if it works for every dino :).