Only instance of 0x7a in my input (sorry I can't supply full sample):

0000030: 6465 828f ef98 c366 2308 0c00 0078 707a

Any advice on how to implement un-implemented opcodes?

Full trace:
  File "javaobj.py", line 36, in load
    return marshaller.readObject()
  File "javaobj.py", line 181, in readObject
    opcode, res = self._read_and_exec_opcode(ident=0)    # TODO: add expects
  File "javaobj.py", line 213, in _read_and_exec_opcode
    return (opid, handler(ident=ident))
  File "javaobj.py", line 365, in do_object
    opcode, obj = self._read_and_exec_opcode(ident=ident+1) # , expect=[self.TC_ENDBLOCKDATA, self.TC_BLOCKDATA, self.TC_OBJECT, self.TC_NULL, self.TC_REFERENCE])
  File "javaobj.py", line 212, in _read_and_exec_opcode
    raise RuntimeError("Unknown OpCode in the stream: 0x%x" % opid)
RuntimeError: Unknown OpCode in the stream: 0x7a