That depends on if you want to go back to the original shoebox style regulator or replace it with a highly integrated modern unit that is about the size of a pack of playing cards. I know there was an ebay seller that was selling new original replacement voltage regulators of fairly recent (1990's or 2000's) vintage a while back, the asking price was a bit rich for me though, I think it was in the $350-$400 range, the alternative is to use a chineese SX460 clone which typically sells for $50-$75 (real SX460's go for $300). Having said this I am not sure off hand what the correct output is, if yours is in the right ballpark the problem may be the rotating diodes, did you follow the test procedures?
Ike