Here are the individual parts you can buy for the 140's mirrors:

http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=140050&M=119%2E970%2C980&GA=722%2E370620&CT=F&cat=19B&SID=72&SGR=150&SGN=05

What about taking it to a welding shop trying a weld on it? That would be pretty cheap to try first.