I'm amazed you need to lock a sliding door on a boat! Anybody bad wanting to get in will use a maul or an axe to get in.
Actually, though, it may be easier in the long run to hire a locksmith to make you a couple of keys for the existing lock.
Otherwise, look at the WM or Defender catalog, and see if they have any with the right spacing or check out a
hardware store or two.
Ann
Ann