I know this is an old post, but if anyone else pops for amphetamine, a good excuse is the medicine Bupropion, it's available as an anti-depressant called Wellbutrin. Even easier to get is the Bupropion+Naltrexone combo for "management of chronic obesity" or smoking cessation, brand-named MySimba.
@MadHatter
Nitroethane and Nitromethane are both used in RC models in "nitro engines", it's something about little cars or whatever the fuck they are that people race, apparently they look for that boost (apparently it destroys the engine over time though?), the actual fuel is apparently used in models of scale 5:1 or bigger. Best bet would be to find a place that you can race those things at and take it up as a hobby, I bet it's just like with bullets in Europe.. you might not have a permit, but if you belong to a shooting club it's no problem to get a case... Nitroethane I have seen listed on the brand-name NIPRON as a fuel-additive AND also as an engine-cleaner and descaling agent.. most nitro compounds could be used as solvents for whatever weird reason I assume..
@Methylamine
Pesticide manufacture.. Manufacture of NMP solvent... Multiple agricultural uses..
Methylamine by itself might be a tough one. Depending on the solvent you use to dissolve methylamine, you get a different compound, so if I was you then I would see what solutions of methylamine are called and then what they are used for, you'd probably get a much bigger list that way and be able to pick yourself an excuse from there much easier.