do you want vanilla, or vanilla custard?
Mountain Oaks Vapor Vanilla Dream is pretty good, and they test for diacetyl and acetylproprianol so it's very safe to vape as well.
Gremlin's Vanilla Overload gets a ton of great
reviews (NOT a custard just a great vanilla vape).
Copper Creek has a great vanilla as well that I used to vape.
Goodlife has one called Plain Jane and it is very reasonably priced, and finally Vanilla Strait from NiteLite which I really liked.