A double boiler is basically a pot within a pot, the bottom (bigger) one containing boiling water. Why not just use 2 bowls, the bottom one filled with water?
Pick 2 bowls, the top one should fit into the bottom one with room to spare. Pour boiling water from your electric kettle in the bottom one, put the top one inside the water and put in chocolate.
I used this batch to put into ice-cream, but you can also put it in pretty ice cube trays to make chocolates. Or mix in some peanut butter and then pour into trays.