i bought mine from rimmer bros. i had bought alloy nipples from ebay but they were rubbish. they were soft and snapped easily,not from over tightening , but even with a liberal coating of copper slip , would not trust them to not snap off like a carrot after being on some time. the rimmer ones are i believe a little dearer , but have two sizes , same thread but longer on the front callipers. i would go for them,but your choice ...
over tightening by garages seems a problem most of the time.