I've done quite a few psychoactive drugs, and I can't say that there is anything that specific. You can't really pick the hallucinations you get. I've had some success influencing them by putting pictures up, but the fried brain goes where it pleases. Still, just looking at lolis while on drugs is an amazing experience.
My drug of choice for doing things like this is DXM (that's cough medicine, ask me if you're interested, I really, really like talking about it, almost as much as I like talking about little girls). It is a dissociative, which is a subclass of psychedelics. They don't give hallucinations like you want, but I do feel much, much closer to little girls and myself when I'm at a good third or fourth plateau, especially when I put stuff junior idol videos on, probably because of the empathetic feelings it enhances. However, the trips aren't hallucinations. I do recall fragments of a sort of waking-dreams that I've had while fucked up where I've lived other lives, sometimes with little girls involved. Even before and after the peak and the trip experience, when the room is completely dark, I've felt girls being beside me and cuddling with me. That said, you will not be able to cum on this drug. (Well, not exactly true, I've done it after about four hours of work, but it was more like being electrocuted without the pain than an orgasm. It was one of the low points in my life).
Most hallucinogens and psychedelics mess with your memory, so don't expect to remember a lot of the trip.
I found LSD to be underwhelming. I've never had a trip where lolis or intense loli feels got involved. There is way too much to get in the way of things like that.
I've never done psilocybin alone, thus have never tried looking at cute pictures on it, but it seems like it would be something really fun to do WITH a loli, not so much to see lolis. The hallucinations for me were mostly distortions of space, but other people say that they see things.
I've had pretty intense intense experiences with MDMA, but not really any hallucinations of people. Mostly like psilocybin, it is mostly to do with distortions in the environment and changing what already existing people looked like. If I ever come across some from a vendor I trust not to give me fucking aneurysms, I'll try doing it with lolipics like the guy you mentioned did. That sounds interesting. If nothing else though, the euphoria would be awesome to have while looking at them. This is another drug I'd like to do with a loli.
And then there is the deliriants. Oh boy, don't do it, for the love of fucking God. You know it's fucking horrible when most drugs in this class are not even regulated by the law. It is the closest you will get to a hallucination experience without having the effects of the trip get in your way. You'll hallucinate people, usually people mocking you, and shadow people everywhere. The one time I made the mistake of taking DPH by itself I legit forgot how to breath, freaked out, tried to run away and ran into a wall and fell down. That does not make for a good experience for someone already panicking. Not fun. The only reason I mention this is because many people say that DPH can enhance the use of DXM, to both ground DXM more in reality and help with the nausea, and to soften the horrors of DPH. You may try that, and I would be interested to know if it helps with the hallucinations, but I'm not touching that shit again.
Now that I've made your thread into my blog post, I'll give you a link to more ramblings: https://www.erowid.org/experiences/exp_front.shtml That site has thousands of reports of almost any drug that can be abused and many that can't safely be. You can browse the experiences of whatever drug you are interested in to see the effects. On the root directory, there is a collections of articles about the effects of the drug, safe dosing, and all that stuff. Or you can just post here. I have nothing to do but get high, fap, and shitpost anyway. I would love to take part in finding a new drug to help with loli visions.