While some care is needed to avoid accidental light leaks, light-proofing a container enough to safely store film or paper is not a colossal effort.

Something as simple as duct tape over a few suitably sized paper envelopes is easily more practical than lugging a Paterson tank.

Black construction paper can make envelopes, or use a maker to darken a typical lighter coloured paper envelope. Apply duct tape and maybe a layer of kitchen foil if you want to be extra paranoid. Two or three such envelopes should keep your material safe from the light.

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Or just use the envelope the film/paper came in... A bit of care with a 'marker card' [or two] that you can easily feel the difference between it and the photo material lets you easily maintain a 'queue' of light sensitive material, without having to lug extra boxes or containers.

Take from the top of the pile, put the exposed stuff to the bottom. Be careful not to turn things over by accident...

Add a few extra marker cards to the stack as bookmarks, and you can even sort your exposures for different development times if you're trying to get really fancy. The important thing is to just not overload your box/envelope with to many/too thick of marker cards such that you risk compromising the light-tightness.

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And in all honesty, keeping track of one box while you're fumbling around with your hands up a changing bag can be easier than a bunch of them, and is faster than swapping things around multiple times for a single reload.

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In short, remember: Layers are your friend when it comes to making something light tight, and you can also make use of your changing bag with a bit of care as the final layer of safety.

Store your film/paper in the first few light tight layers, and then stow them off to one side of the changing bag that you wrap up as a neat little package when you're out and about. Use care with how you're transferring things in and out of the bag, and think about not only keeping the light out, but also keeping the dust out too!