Costco currently has a Water Ridge dual-flush toilet with a $15 Mfr instant rebate attached to it. It's normally $99.99, now it's $84.99. I'm pretty sure this is the same model local (IA/WI) Sam's Clubs are carrying. The models at both locations look identical. There's a silver flush "button" on top of the tank for the 1/2-water flush. Sam's charges $100 as well. At Costco, it's item # 360380. The instant rebate ends 11/1. This isn't available online. There's only one dual-flush toilet on their site. It costs $349.99.
I saw this deal in the Des Moines store. Has the look of a nationwide deal (same as the Sanyo Eneloop batteries), but I'm sure there are plenty of wharehouses not carrying it. The post about this toilet at Sam's Club started a year ago (http://slickdeals.net/forums/showthread.php?t=943776
). I only noticed them at local Sam's wharehouses 1 month ago (i.e., other parts of the country are ahead of the midwest...are no longer carrying it...we just started).