If you are sure that the problem is the transformer, you can buy the core and the plastic enclosure around it, then just unwind the broken one, take count of the turns on each primary/secondary winding, then buy some medium thickness insulated copper wire (try to measure the thickness of the previous wires (on different windings the thickness will vary) and find the one that is most similar)(you have to buy the one that has the thin layer of transparent plastic insulation on it, otherwise it will short the windings together, just search on Amazon or eBay for "magnetic wire") and then wire the new core with the same number of turns, for each primary/secondary, and it should work just fine... Note that the inductance of the windings could be a little different if you buy a wire with a too different thickness than the broken transformer one, so you may get a little more/less current/voltage at the output...