Link: https://www.amazon.com/Amazon-JK29LP-Glad-Dash-Button/dp/B0155NGW12/

Edit: Glad button back up to $4.99.

Tide Dash button is $.99 for one day: https://www.amazon.com/dp/B0187TMRYM

Edit: Tide Dash button sale is over

IAMS button is $.99: https://www.amazon.com/Amazon-JK29LP-Iams-Dash-Button/dp/B01N3Z49V2/