EZ-Up brand Deluxe Weight Bags.
Very well designed and sturdy. Filled with pea gravel. I have 4 of them. Price: $50 Excellent condition. (If bought new: $90 plus shipping. Plus cost to fill them.)
The handles are very functional. Bags strap to canopy legs, or lay onto horizontal stabars of Trimline canopies.
See product at website: