Go to sheria house.They have original copies of all marriage certs.(don't ask me what original copy is,Iko.)
You will be given a form to fill in your details after parting with a small fee,don't know how much.
Next you will be asked to pay a 'search fee'
That is for the fellow who will go into the archives na zimejaa kama kuni.Hata ya Lord Delamere iko huko.
Once traced you will be given an original copy and go home smiling.

How fast depends on how hungry the search fellow is.
good luck