Industrial_Girl, I've been buying corkbark from
www.blackjungle.com for a few years now. I'm a bit of a nut about corkbark. I've always ordered it, but the last time I bought some (July) I physically drove to the place and hand-picked out the pieces. I wound up spending a little over $100 on corkbark and driftwood, and that was with a 20% discount(!) and a cut rate per pound because of the number of pounds I bought. I will be experimenting with different basking areas this fall. The longest piece I bought for Tilly's outdoor stock tank is 36" and does look like a log.
If you want to buy corkbark for Sheba, you want to get a "curl," not a flat piece. The curls tend to flatten out over time (but never become completely flat), and with a curl, you've got a built-in ramp for the turtle.
I've never had a problem with corkbark being eaten. It's been nibbled on a few times, but I just take that as an indication that perhaps a bit more food is needed. Poop will float sometimes, and it's not because of corkbark.

"You become responsible, forever, for what you have tamed." -Antoine de Saint Exupery-