I made a wooden toy version of a Thompson for them to play with. Then I had to make another one so they had one each.
It's just a bit of wood, with a couple of bits of metal. But I got the design sorted out so that the magazine (also wood) can be removed and replaced then not fall out while they ran around with it.
So with one moving part and a bit of imagination it's easy to do.
Again let me know if you're interested in making your own and I'll post an instructable.