If you're going the OTC route, you're more or less krutzed IMO. It's all garbage.
Pseudoephedrine doesnt have any mental stimulation effect.
Ephedrine has way too much in the way of physical side effects.
Those herbal things are a real crapshoot, but most of them are garbage, and usually the active ingredients are ephedra (ephedrine + garbage), caffine, and stuff that doesnt do jack shit.
Party pills with BZP are great if they're legal where you are.
Propylhexadrine had, for me at least, negative physical side effects that outweighed the positives, even at small doses, and i couldnt focus worth crap, was just bouncing off the walls, heart bouncing out of chest, then crashing, and i since i played with it (a couple inhalers worth over like, a month), i've had occasional palpitations.
RC's give you some good options, but they're grey in terms of legality.
Mephedrone is more-ish and has had some horrifying side-effects.
Methedrone sounds worse than meph but with even worse side effects. (not touching this or meph with a 10 foot pole)
MDPV might work, if dose was controlled carefully
Methylone may not be what you're looking for, but in small (really small) doses, i find that it wakes me up and puts me in a good mood, without doing much else. Butylone, same deal most likely (havn't tried it yet), but might be better as it's generally said to be more of a stimulant...
Dimethocaine, i havn't looked into, but if it's coke-like, it's probably not the right kind of stimulant.
I've tried mdpv and amphetamine for being wakeful and focused at work, but neither of them, imo, is that great at this. For me there doesn't seem to be a medium between "groggy and unfocused" and "too hyper to focus well" - stims never seem to work well for me if i'm just sitting in one place though (as is the case in many jobs nowadays).