If the time period is right, one place to potentially obtain copies of marriage and vital records is in military pension or other military benefit records. Widows would have to prove their marriage to the soldier in order to receive their pension and birth records for children of deceased soldiers would also have to be submitted–if those children were under a certain age. In some cases, the original record may no longer be extant and the copy in the pension may be the only copy.
If you received a copy of a vital record from a pension file, indicate that the copy you have was made from a copy in the pension file. That doesn’t mean it’s not a valid copy–it’s simply indicating where you obtained the copy. That way, if the originals are no longer extant, other researchers aren’t left wondering “where you got it.” And you know for yourself that the copy you got didn’t come from the courthouse either.
That way if there’s something you don’t understand in the copy of the record that was in the pension, you know that you still may need to see the original.