Hi, and welcome to the forum. I've just been through the same sort of thing myself with my first colonoscopy, and the thought of taking the prep (not Moviprep, I have to say) filled me with more fear than the thought of what the procedure might find, because vomiting is something I've always lived in dread of also. I sort of have an advantage in that I'm a health professional, but having spent many years trying to reassure and advise patients taking bowel prep about vomiting, only to see them bring it up anyway, it helped to get my anxiety levels up nice and high beforehand as I was sure I was going to.
As it turned out, the preparation I took tasted less bad than I'd feared, although it wasn't the kind of stuff I would want regularly. I still felt like retching a couple of times while I was trying to drink it, but I managed to put it off by deep breathing and taking lots of sips of lemonade.
You can't guarantee that you won't be sick, as far as I can see, but what you can guarantee is that if your prep isn't full enough then passing the scope will be a waste of time, and you won't be able to have the procedure until you've completed another round of prep - I know it isn't very helpful, and I don't know if doing what I did helped me to keep it down. As I said, I totally dread being sick, and deep breathing with sips of lemonade is what I usually do to try and avoid it. I can't guarantee it will work for anyone else, I just know it works for me, as I hardly ever vomit when I'm unwell (twice in 20 or so years.) If you're anything like me, you'll have strategies to put off the actual act of vomiting anyway - try working through them. It will be worth it if it means your bowel will be clear enough for the scope to see.
I'm sorry I don't know anything about alternative preparations, and I've only ever tasted the one I had to drink. I couldn't even begin to give you any taste comparisons between the one I had (Picoprep) and the others that I've seen used.
Sorry if that's not encouraging, but from where I see it, there is no magic bullet that guarantees you won't. If you're as scared as I was about it before I drank the prep, then I don't envy you.
I hope all goes well for you next Monday