Gotoh's direct replacement U.S.A. Nashville bridge seems to be gone from their Website. Perhaps it has been discontinued, or is in the process of being redesigned. It is listed as out of stock at several of my go-to guitar parts retailers. Allparts say they have it in stock, though:
https://www.allparts.com/GB-2540-003-Gotoh-Black-Nashville-Tunematic-Bridge_p_1616.html. However, the matching tailpiece is listed as out of stock. OTOH, Guitar Parts Resource lists the tailpiece in stock, but the bridge out of stock. I haven't dug much deeper than that, but I'll bet if you really dig, you can find a retailer who has both in stock, so you don't have to place two separate orders and pay two shipping charges. You might also try e-mailing or calling Guitar Parts Resource (or Allparts) to see if they can get the out of stock part in; I have had luck with that in the past, getting them to order me stuff that was listed as out of stock on the Website for many months. If all else fails, try Amazon and E-Bay. It should end up running you about $75–$80 plus shipping for the set.
You can also ask a local plating shop to re-plate your stock hardware.
You don't need locking hardware unless it somehow makes you feel at peace. I'll take it if it's there (like on my Dean Z and my G&L Ascari), but I won't pay extra for it.