From what I remember hearing, conditional ordinations are/were kept very hush hush, so you may not be able to obtain contact with any "witnesses". Much less "certificates". You be better off hunting down the administering bishop to confirm it.
From what I understand, you dont get a "certificate" for conditional ordination, confirmation or baptism since its given under the pretext that you were not "certain" of the first one. So the original date and cert for that sacrament will be the only one a person has. Can you imagine having two or three baptismal certificates from different periods of your life? Sounds a touch wacky to me.
My Father has conditional confirmation, he didn't get a certificate. I dont the such certs are in existence.
The Orthodox probably have such things, since every sect in schism with the others wants to re-chrismate you when you come to them.