Rob - if by "CAN be reused" you mean not corroded - then WD40, parts cleaner, soda blast, etc. can work - but you may want to then strip the cleaning agent with acetone/etc. & send them out for replating to gold Cad or Zinc per original finish on them. Sept. 2010 "Auto Restorer" has a good article on bolt types & strengths & markings thereon FWIW. Otherwise if corroded then, I agree with Mark if they're available today - but make sure you're matching the correct type/size/finish & strength as used with OE.
Mark Heard has told me that you can add them to a PMB caliper rebuild order & Eric Shea will send them out with the appropriate type batch replate when he does his caliper resto's - otherwise a local plater can do them - but check price vs. new as they may be the same or close enough to not warrant the time & effort - even if it's for Dad's 914!