The MS21250-04??? is the same bolt with different head markings.
By looking at the prints they appear identical, the custodian of the specs were NAS and MS(US GOVT), other than that I don't see any significant difference.
If the sizes are common, they won't be a fortune, if they're not .they will be a fortune. This is true no matter what spec you start with, AN/MS/NAS/OTHER.