I have large refreezable ice bricks that come with weekly meal kits delivered to the house. They stay cold for a really long time, moreso than the standard blue gel bricks. They're obviously handy for picnics/coolers, but I've heard they're great for fishermen coolers too!
I get weekly meal kit deliveries, so I always get at least 1-2 every Wednesday but I may have more from previous weeks. Take however many you'd like that I have.
Pickup in Franklin Farm community of Oak Hill/Herndon, 4 miles north of Fair Lakes/Fair Oaks and 4 miles south of Reston Town Center.