You have part of that backwards:
Grin's spokes are all custom-cut-to-length; just put in the length you need. They don't have ready-made ones.
http://www.ebikes.ca/shop/electric-bicy ... pokes.html
They'll also build your wheel if you want, though I don't know how good they are at it--I just know they're good at cutting the spokes the length you want.
FWIW, regarding the other place: if they're custom-made, then they wouldn't "have" any variety of them at all.
If they *just* "have" a large variety, then they're not custom-made. They could do both, have a large variety of existing spokes, *plus* custom-make others, of course, but that's not what your statement says.