maybe you won't find them at the grocery store (maybe by the fondue sets?) but you will find hexamine tablets at the surplus/camping store. when you do a MeAm from hexamine w/ HCl, you get as much AmCl as you do MeAm. at the 1000g hexamine scale, after the initial reflux, a vacuum filtration nets you around 500g of AmCl, and, later on, about 500g MeAm.
Post 323193 (https://www.thevespiary.org/talk/index.php?topic=8905.msg32319300#msg32319300)
(RoundBottom: "Chromic’s Methylamine.HCl", Methods Discourse)