Johnnie Walker isn't bottled every year like a vintage wine and actually a couple or few years might pass before new batches of all of their marques are released. This could be pretty tough for you to find a JW Black 1977, but try e-bay. Or, maybe someone might chime in here with another or better suggestion.
The new batch of Johnnie Walker Black came out earlier this year (in the new package) and it'll now be a couple of years before another bottling takes place.
Good luck to you and congrats on your upcoming nuptials!