Deal Genius offers the Cozy Chair 15" x 15" Outdoor Memory Foam Chair Pads with Ties 4-Pack
in six colors (Aqua pictured) for $24
with free shipping
. That's $26 off list and the lowest total price we could find. They're UV-, fade-, mildew-, and stain-resistant.
Of note, they're available in 16" x 18" for $5 more.