One assumes these are fiddle bows????

What does the government have to do with Denver Airport?   Nothing....

Ummmm.... There's a place where one can buy bulk guitar strings.... if you buy enough of them, they throw in a rigi9t plastic tube with a carry strap attached.... I wonder if maybe you could approach them, buy a tube or 3.... Then ship the bows in those, providing pre-paid postage so that the recipian could ship the empty tube back to you?????   

No pic., but url....
http://www.stringthis.com/ststtu.html

Or how about this? Make your own tube out of PVC pipe fittings.... include return shipping or, tack the cost of the PVC onto the price of the bow????