Some strong shockcord and a Nexus Springlock cord-lock will see to the attachment. Put each end of the shockcord through the cord-lock and knot it so you've got a loop. Feed this through your pack's small loop, then wrap it around the poles, push the cord-lock through the shockcord loop like a toggle, and pull the ends tight. Carry them handles-up - there's no way they'll fall out and it's also safer for other folk!
If I haven't explained that very well then take a look at the PODsacs website - it's the way they've done their ice axe shaft attachments for years.
http://www.podsacs.com/products_blackice.html
I guess the poles might swing a little from the small loops - but you could always run another bit of shockcord across the pack horizontally betwen the small loops and push the poles behind that before you secure them, that should keep them stable.
You can get the necessary shockcord and the right cord-locks from Needlesports - just scroll down here