Scared of buying an AE that is “fake” or has something else in it that will cause me terrible side effects

[Tricondyla ledouxi]

So I need some AE sources for the UK but I'm a little worried. I figured I should get the AE before I even get the SN as I've heard AE is even harder to get than the SN itself. I already have an SN source so don't worry about that. But I REALLY need a RELIABLE antiemetic source. It's not really about losing my money to a scam, though that would REALLY suck. It's more about the fact that I am scared I will order an AE, it will arrive, I will take it and it will cause some terrible side effects because of it being fake or something else being in it.