I just recently fell in love with them too! I am on a mission now to make my whole stash of needles bamboo. I don't think I have come across anywhere that has free shipping though, although I have seen a flat rate of $4 so I figure if I wait until I need some other things and then order everything at once, it will be a pretty good deal. If I can't wait I am fortunate enough to have a LYS that I can run to and see if they have what I need.
I do have a Joann.com coupon for free shipping and I think they carry bamboo needles. The coade is NEW60305 and it doesn't expire until March 11 and there is not a minimum purchase necessary.
Hope that helped you some!