You could buy all the sleeping bags from Goodwill and bring them to your local unhoused advocacy org
In the US, military surplus stores would sell new overstock as well as used gear from people who are no longer active. The utilitarian and frugal choice was to visit an army surplus store. Surplus stores sold all sorts of goods, but this is probably best encapsulated in the M-65 fieldjacket.
Vietnam anti-war activists reappropriated the M65 jacket, but outside of that, it was a symbol of frugality. (Much like the NHS circle glasses, worn by John Lennon, Harry Potter, Gandhi, etc.) Charlie from It's Always Sunny in Philadelphia wears a jacket much like the M65, playing on the viewers conscious or subconscious association, to play into his unclean and disheveled looks.
But these surplus stores also sold bags, clothing, boots, and, importantly, sleeping bags.
But as US Military moved from large surplus orders to made-to-order manufacturing, overstock started to dry up. The military surplus store is dead.
Over this past month, at least two people froze to death in my city.
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When I am doing my Travels, I hit up Goodwills along the way. It's one of the thrift stores which sell more than just clothing. Being already 30 minutes out from the city, I'm saving an hour someone would need to go to Goodwill and search.
The US military has a really nice modular sleeping-bag system. For all the cool experimental "this sleeping bag is a tent!" "this jacket is a sleeping bag" systems, none of them beat the US military's modular sleeping bag system.
But, again, the surplus store is dead. You'll pay upwards of $150 for that now. The only reason to purchase it is familiarity.
So, I just got a sick score from Goodwill: Three bags for $32. I don't know their heat rating and I don't know what they're filled with.
I have a connection at a local unhoused activism org who took these, washed them, and have given them out to people already.
The unhoused activist org I know about is a good one- they do direct action and many of the people in it are unhoused themselves, or have been in the past. They are knowledgable. But you can also just give things to people directly if you prefer.
(p.s. if you, like me, have too many reusable shopping bags, then you can also give these to people. people love these)