I've got quite a few 40 hour heat packs. I'd be willing to sell you some for what I paid...$1 each, but I'm in Joliet so it would either have to be a road trip for you or I'd have to ship them. LMK
Jeff
If you don't need the longer lasting ones, I've seen up to 18 hour ones at Walmart and even at Menard's. At walmart they're usually in the camping section. I hope this helps.