Using a candy dish, a fan from an old computer, 2 fridge magnets, a variable resister (old radio volume control), a toggle switch, a 9 volt battery and connector (old radio), some wire (old telephone wire), 4 screws and 8 nuts I was able to build a stir plate. Every part was found from thrown away items and electronics.
The only tools used are drill with bits to cut the holes for mounting the fan, mounting the switch and mounting the resistor. 2 small files, 1 flat for the surface and 1 round for the edges of the holes. Soldering iron for the electronic connections and contact cement for the magnets.
It works well. You can find other directions for building a stir plate on the internet. What I did was very simple, about an hour to put together and totally free.