Unfortunately you might have to spend a few bucks, but no more than that, and you'll have yourself a solid piece of smell-proof equipment. Of course everybody has their preferences, and can say they've smoked than anyone else on the forum blah blah blah etc.. But I've used mason jars, Tupperware, glass-on-glass containers, pill bottles, and so on and do forth.. all of which eventually developed some sort of smell eventually. The only thing that I have found to be truly smell-PROOF is a coffee thermos. One with a sealing cap/stopper and a lid that doubles as a cup (for example, a Stanley brand one works perfect). If you don't want to buy a new one, a little patience and perseverance (or luck if it's your first trip) and you can find one for a few dollars at a thrift store.
I never have issued with my room smelling like weed when I leave it in my drawer in a bag. Usually it's in a jar though