http://importnut.net/imports.htm
Also, heavy throttle sells brembo blanks already drilled for 4x114 bolt pattern at no extra cost.
If you can swing it, get a MC for a non-abs Z and you'll have the center flare seat already in the master cylinder. If the car is ABS, then you have to slice up the old S13 MC to get the seat out.
And if you don't mind not having the best of the best MC, get the 1" valved Z MC, as I believe they all had the center seat.
Again, please please please please search. This topic is so overdiscussed, it's not even funny anymore.