Hello Matt,
cost for a brass plate is 55$. We can also make a maple plate for you for 250$ , but probably it would look a bit odd, since the finish on the bass is obviously older than the finish we would put on the new one; also the grain wouldn't match that of the back of your bass; Mica & I discussed this and thought of suggesting using a different wood, perhaps Ebony like the top & headstock, or possibly purpleheart like the neck laminates.
Valentino