Got one at an estate sale and took a chance charging it with positive tip and it worked. I used 4.5 vdc @ 500 mah with positive tip and it took about an hour.
If you have the soldering skills then definitely but do not forget to insulate the area so the solder or any bare wire do not come into contact with anything.
Any place including Amazon or Ebay that sells the WLToys V949 motors. They are a perfect fit when fully seated and have metal cogs instead on plastic ones but they need to be fully seated .