I'm using the local greengrocer more recently, and get chatting to the staff, brown paper potato sacks tend to get dumped, mushroom blue crates, tend to get re-used by taking them back to the fruit & veg market, but of no benefit to the shop owner, so they are happy to give a few away.
In desperation a few old pillowcases, wrapped in dark breathable materials, such as towels or old bedding are preferential to storing your spuds in plastic.