Searching for vibration damper/harmonic balancer for M103

[dirtysocks]

Anyone know where I could track down a new vibration damper for an M103 engine? I.E. the metal/rubber disc behind the crankshaft pulley. Mine is sheared in two and rattling quite loudly. Or even a part number for it maybe?

Also, what actual purpose does this part serve? Engine seems to run fine with it busted, other than the obvious noise. Am I in danger of damaging crank if this part is faulty?

Thanks for your time