I have bought a few items on Alibaba, and always had a good experience, so far. However, they are a marketplace, not a department store, so who knows how well they police their participants.

At the low currents you're dealing with, even if the Vregs are fakes, as long as there is a Vreg in the package and not just empty packages, you're probably okay. They might be rated for a little lower power or have a slower response time, but as long as they hold 2.85V closely, you're probably okay.