Where to buy an how to heat treat VG-10 aren't really trade secrets. It's easy enough that even the Chinese, (who are good enough to make iPhones) can manage it.
and yet only ryusen (same folks that heat treat hattori's vg-10) and takeshi saji does REALLY great vg-10
they are masters of vg-10. only folks that know vg-10 literally by heart. only folks i know that do vg-10 perfectly right.
most vg-10 get really sharp, hard (harder than most stainless) to sharpen, edge retention is from really sharp to so-so quickly and stays so-so forever....
hattori / ryusen's vg-10.... now those are easy to sharpen and has better edge retention than the rest
at least from what i've read