Spoke Nipple bit size?

Greetings, looking to lace my first rim on my 2012 R and I can't seem to find the right bit size to use on the factory nipples.

It's a square right? I have a number 3 but, I've looked all over the internet and can't find one.

Anyone have an idea where I can buy one?

thanks!

I have several Hozan spoke wrenches, their #9 fits a WR.
I think the nipple must measure about 5.75 mm. A 5.5 wrench won't fit and a 6 doesn't fit as tight as the Hozan #9.
The wrenches I have may not be available any more, they seem to have gone to the bicycle side of spokes adjustment.