Maeng Da kratom is my personal favorite "stimulant". Technically it is more of an opioid but it feels pretty speedy. People who I have given it to seem to agree. I'm not saying this to be facetious, I don't think there are great stimulant RCs and most stimulants are pretty harsh on the body too... Anyway, it's worth a shot for sure, especially since you're talking about long-term dosing at smaller doses.
While Kratom, in general, is great and has a variety of uses, I'm not sure it'd fit his criteria. I love it myself, yes especially any more stim-like Kratom for sure, maeng da being a top choice in that respect. To note, I've tried a doozy of Kratom vendors and strains and while always consistent in a way, it varies to a degree. No Kratom strain, imo, is an actual functional *stim* herb/product. Just some of those effects, characteristics, mildly presented. Anyways while Kratom produces a pleasant experience overall (always has a mood lift and boost!) it's generalveffect profile "does" hit the mark for some people. I find it far too inconsistent on the basis of stimulation, and true energetic and the focused behavior it can create. YMMV, as always. And no I'd never bash Kratom, at all. It's miraculous to a degree. But if one wants to be truly productive and stimulated in a classical sense, look elsewhere. (As in other rcs, the bad stuff.. yeah.) Don't have a list of rc stima on hand, they fade in and out of the market pretty quickly/consistently.. (Hmm I wonder why?

) but... maybe 2-fa, 4fa, some more I can't recall, etc. Fluromethamphetamine, and ones like this. And yes they sound risky, and directly 'tough' it can be worth the hassle of payment stock availability and so on. But there's always an associated risk here though. Say you do get the stim/product that checks off the boxes, don't expect it to be a long term solution both in toxicity and the like, or more so constant vendor price hikes, removal and other nonsense. Any med change or thing you seek out requires extensive research or knowledge on most don't care to do. Pm me if you need some advice.