If you're still looking for carpet tubes, go to any home supply store (Menard's, Blowes, etc) or a local lumber yard and ask for Sono Tubes.

8"-16" diameter cardboard tubes used for pouring footings of concrete. Waxed, they hold up for months and are cheap (12" x 48" was about $5 last time I bought them.)

I only hadda use about a 6" piece to hold down the average xmas tree (maybe 15-20 lbs of crete).

In a lifetime, the average driver will honk 15,250 times. My wife figures I'm due to die any day now...