I had a problem finding just one also. So I looked up a local farm poultry swap, and that's where I found Cas. My friend got 2 ducklings, and I got Cas (who for a day I thought was also a duck but quickly realized is really a goose lol). Her ducklings bonded with each other and wanted very little to do with her, so she finally ended up re-homing one of them. Cas on the other hand, has been and continues to be, completely bonded to me and loves any other human he meets. Based on my limited experience so far and the research I've done, if I had to choose between a house duck or a house goose...I'd say goose because they bond (imprint) stronger, in my opinion.
You could also try calling your local feed stores. Some of them order chicks and ducklings/goslings and you could get just one. You can also check the forums here to see if someone near you has babies, or look up some farmers around you. I would suggest you find one (whichever you choose) as young as possible (ideally a day old or so) if you wish to have it imprint on you. I'm no farmer either (although I was in the past). I live in the city and Cas lives in the house. He is out and about with us all day and is now wearing his diapers which make that a cleaner experience. When he's put up in his little house (a converted dog house) at night, we take his diaper off and he snuggles with his stuffed animal toys. He's not lonely or bored or sad that he doesn't have another goose to cuddle with. And with him we've actually found that he doesn't like other fowl! He is perfectly happy hanging out with his people and everyone in my house spends time with him.