Stainless..A taboo subject for some but manna from heaven for others....I bought some nuts and other fasteners from the company shown below recently and was impressed with the quality...Bar turned to the correct Cycle thread nut pattern etc...They also provide a service making 'custom' brake rods to your dimensions...Very handy....As well as nuts and bolts they have some other useful fasteners so they are worth a look...Located in Lincoln UK and I have no connection with them other than as a customer...
Acme Stainless..01526 861991....or on t'internet....Ian