Yup, but the same laws of physics also mean that a wider pump will require more force. And with a smaller handle, that'll probably get really annoying really quickly!
Heh, well, laws of physics state that if the pump is smaller then the barrel space will be smaller and it'll take more pumps to pump in the same amount of air - unless it's using a one-time thing like a compressed air canister, or is battery powered or something.
EditL Though it's worth mentioning that modern material allow them to make the barrel walls thinner, and for them to make wider barrels than they used to, thus allowing them to make shorter and/or smaller pumps that are just as effective these days. Not sure how much you'd gain from modern materials though - I'd guess you'd only be able to make it 75% of the size or something like that.