Funny you should ask. I was wondering the same thing, and then decided sending just a rhyzome just didn't have the same effect as a pitchering plant. So I photographed my packing, step by step. This should give you some ideas.
One Sarr, carefully re-potted into plastic shipping container.
Used soldering iron to melt slot, then cut slit to put over pitcher base to hold soil in place.
Note it's on upside down.
Second lid with hole (cut with soldering iron) to fit over pitcher(s) taped to tube.
Second lid and protective tube snaped on container over upside down lid.
Outer tube to place over entire plant. (both tubes made to custom fit from a priority flat mail mailer)
Bottom piece ready to slide under and tape on outer tube, top lid ready to trim to size.
Packing added between tubes to stablize.
Packed into a Priority mail 'shoe box shipper', with lid taped on and ready to ship.
Total weight was 9.6 oz., well under the 1lb minimum shipping cost. The Sarr arrived in
PERFECT shape.