A lot of people (myself included) are huge fans of the quizzes on Pottermore and the results they get from them. Pottermore offers a LOT of Patronus possibilities in their quizzes so I'm not suggesting that every single one be available for purchase, but I think a lot of people would be more interested in forking over the money if they could buy their Patronus.
For example, the most common Patronus that people get from Pottermore is the dolphin. My Patronus is an eagle, and I know more than one person with a calico cat Patronus. I think just by adding well-known/common animals, a lot of people would feel more inclined to buy a guardian from the store.
For example, the most common Patronus that people get from Pottermore is the dolphin. My Patronus is an eagle, and I know more than one person with a calico cat Patronus. I think just by adding well-known/common animals, a lot of people would feel more inclined to buy a guardian from the store.