Hmm, I don't think I would dose on morning glory seeds unless I knew the exact strain.
For example, some strains like HBWR you only need 4 or 5 seeds to trip hard, whereas other strains you need to take upwards of 200 seeds at once to trip.
So you can see why trying to dose an unknown variety would be tricky.
You can easily find seeds on the internet like others have said. I'm partial to HBWR myself. They're the most potent and you hardly have to take any.