I think I can remember that the Ivy leaf varieties don't conatian significant amounts of alkaloid, but thats just from memory, there are loads of something similar growing where I'm living at the moment, but haven't bothered investigating.
I've tried common morning glory (purpurea) at 200 seeds without effect, but 100 tricolor do the trick just fine. Very easy to get hold of in (semi)bulk too. Back in britain I got hold of 1500 seeds for £10-15.