I've created a perma-pre characted called Time Traveler Gwen who is just here to kick some Charr ass and it would be tight to actually have the Gwen tonic to go with it. The only problem is I haven't seen anyone offering one in pre and I'm probably too broke to afford it anyway. I've got 19e in my storage in post that I'll gladly trade you for it. If 19e isn't enough, I can farm some more nick sets to sell for more.
EDIT: Someone from Reddit hooked me up! Thanks y'all!