Ebay offers Embark Shelter Anchor Weight Set for $23.99 (reg $39.99) with free shipping.

Product Description:
Stay prepared on any outing with the 4-Pack Shelter Weight Set from Embark️. The set includes four 5-pound concrete disks coated in plastic for lasting outdoor use. These weights help anchor canopies in windy conditions and secure to poles up to 1.25 inches in diameter with a handy flip clip. The rust- and weather-resistant weights fit most standard shelters and are a great way to secure your shelter at the park, the beach or in your own backyard.
Embark: Find wonder as you wander.

• Dimensions (Overall): 1.82 Inches (H) x 9 Inches (W) x 8.9 Inches (D)
• Weight: 5 Pounds
• Assembly Details: No Assembly Required
• Includes: 4 Ground Anchors
• Protective Qualities: Rust-Resistant, Weather-Resistant
• Material: Plastic