Stock Port via Amazon offers Prime members the Greenco Super Strong Foldable 11" Step Stool in Blue or Green for $10.99 with free shipping. (Black is available for a buck more.) That's the lowest price we could find by $3, although we saw it for a buck less last month. It features a carry handle and supports up to 300 lbs.

Update: The green stool is now available for $9.85 with free shipping, without the need for a Prime membership.