SRU: Or something...

Okay just been thinking about SRU and the various different version in different fictions. Terry Pratchet has at least one interdimensional shop. The well known one of the title. But where did it all begin?

I seem to remember an old SciFi tale which had an interdimensional weapons shop, I think it was a short story, but thats as muchh as I can remember anyone else have any memories or knowlege of where this phenonomon comes from? (spelcheck doesn't work :S)

JC