the ldif utility provided with OpenLDAP" - which the latest OpenLDAP
Or just read the ldapmodify/ldapadd manpage. The jpegPhoto example in the manpage shows how to load a binary value. You can load DER format certificates directly, this way.
I agree with Howard, you don't have to use ldif command. You can use ldapmodify or ldapadd to achieve the same thing. I have a working example I could email to you, if you are interested.
Cheers.