Most states in the U.S. have organ donor registration available at the Department of Motor Vehicles. By adding bone marrow registration, with accompanying educational material, thousands more donors could be added to the registry.
I like that this idea is sustainable in the sense that the stores add value to what they provide by participating. Just as you've pointed out that stores have specialized sections devoted to niche markets, the 100km would be its own marketing. Of course consumers would have to be educated, just as they were about organic, non-gmo and gluten-free food.
My only concern with this mode of integrating local food is that vendors can, and usually will, charge a premium for specialized products. I would hate to see local food included in supermarket offerings, only to have it priced out of the range of the bulk of consumers. This structure can make it especially hard for low-income consumers to have access to the "special" food. Perhaps the government could offer other incentives for markets, especially ones in low-income, inner-city communities, to include a 100km section.
I think you've touched upon something very important with the "fortunes that you have as examples; the religious community. Why not take this a step further and develop religious organizations as partners? The imams or priests could explain the importance and moral imperative behind donation. They could also distribute swab kits to a targeted audience.