Not sure what 'Acetylpyrazine' is could you describe it so I can try something that it is in to see what its like?
I can't really point you towards any premixes. It's likely you've already vaped multiple flavors with AP in it. It's a very common additive. It's simply a nutty/bready note. Like hazelnuts or almonds combined with what tasting fresh bread smell would be like (if that makes any sense). A lot of DIY guys use it in their dessert flavors.
It's super cheap and little goes a long way. You could take 5mls of your favorite tobacco and just add a drop or 2 and see what you think. Too much will ruin a blend but a touch adds a whole new dimension to the flavor.
Perfumers Apprentice - Acetyl Pyrazine 5% PG