Old fire alarm guy is correct that there is nothing magic about the factory installed bridge rectifier. Most manufacturers use a hefty bridge rectifier rated for 3 or 4 times the expected current needs. That makes a good safety factor for surges and bridges are not expensive. Find a 100 volt 20 or 30 amp bridge and it will work. If you do not have the harness it will take some detective work to determine the connections.
I have the wiring diagram for the bridge rectifier and harness colors. The problem now is finding the Molex connector for it. It's 4 pin and evenly spread out, nothing weird, is there any wire harnesses already pre-made with that type of connector?