Disappointing answer: in a shop.
To be specific, a Farm Shop - a term which probably needs some explaining (UK; not sure what your local equivalent would be). It’s not like a factory outlet (though see below) - it’s more like a deli in a country setting. This is the particular farm shop where I discovered the medlars, right there in those baskets out front - I bought some because I had no idea what they were and had never seen them before in my life. BTW, that farm shop’s mission statement (kinda) from their website is:
Village Greens specialise in selling fresh seasonal fruit and vegetables, including our own grown from our Victorian walled garden at Denbies and our growing fields at Ockley. You can shop for a meal to cook from scratch, local wines, specialist food ingredients. Have confidence in knowing that our priority is for our products to be local, natural and ethical. We use traditional growing methods and do not use artificial pesticides, insecticides or fertilisers. We also stock the best local artisan products…[list]…In fact we sell over 60 products sourced from within a 20 mile radius of our shops. Why not check out our local food and cheese maps in the shops.
IIRC, the shopkeeper said that the medlars were grown by someone in the village who had a couple of trees. I really hope that’s true. I think it’s fair to say that Ockley Farm Shop is doing the best job of any in our area.
I didn’t buy enough medlars to make jelly but, as noted in the Coelacanth Jam thread, by weird coincidence I just happened to stumble across a tree in a community orchard, and picked up some windfalls. What I didn’t say was that a few days later we found yet another tree, in the gardens at Nymans. You get the impression that, pleasingly, there are enthusiasts with an interest in keeping medlars going.