Foolestroupe is right, of course, but it might be that Mr Happy is thinking of a player who uses a bowing technique (frequently encountered among those who've never been "taught") where only a few inches (cm?) in the centre of the bow is actually applied to the string. For such a technique I suspect the bow from a half- or even a quarter-sized violin might be adequate. If the frog on such a bow is too small I dare say one could buy a cheaper full-sized bow and get a repairer to cut it down to size for travelling purposes, while keeping a proper one for normal use.

Cheers, Rowan