Is there a pre-cut 5-string nut, 10mm spacing?

[Zapp]

guys I'm lazy and trying to save some time & effort.
I want to replace the nut on my Classic Vibe J bass with one routed for 5'string with the high one cut off [i can do that part].
the string spacing on the stocker is 10mm.
anyone know where I can pickup a high quality 5-string nut with such spacing?

and, if I end up needing to whack on this stock one, what tool do you recommend to widen the openings without too much danger of nicking them any deeper -- they're the right depth already.