Sous Vide Weighted Magnets to Weigh Down Hop Sacks, 2 Count
Weighted food grade magnetsMore Info
These are generally intended for use in sous vide cooking. However, they look like they would work well to weigh down hop sacks.
Note that this is for a total of 2, other count options are available.
Sous Vide Magnets to Keep Bags Submerged and In Place | Sous Vide Accessories to Stop Floating Bags and Undercooking – Great Alternative Tool to Sous Vide Weights, Balls, Clips, and Racks (2, Red & Black) – note that multiple variations of this product may be available, as such a different version may appear at this link
Shop Around… Search Amazon for “sous vide weights”