Beilstein Crossfire said it was sold by Aldrich as 48,389-3 N,N-Dimethylmethyleneammonium chloride, CAS [30354-18-8] - it is the chloro analog of Eschenmoser's Salt, which is the Iodide.
Beilstein only listed really yummy synths, such as the reaction of Me2NH with Cl-CH2-O-SO3H and similar toxic, corrosive and carcinogenic brews.
You probably didn't find it as Chemfinder didn't check for the methyleneimine tautomer.