Chocolates can be obtained from grocery stores, specialized chocolate stores, and other types of stores, including online.
There is one supplier we use more than any other for chocolates, the same store where many of the Amish buy chocolate for making candy. The supplier is Walnut Creek Cheese. (Walnut Creek is the name of a town in Ohio, USA.) Walnut Creek Cheese sells more than just the cheese the company name implies.
Their website is WalnutCreekCheese.com
The Blommer chocolates mentioned in this book (Blommer Kreemy White Chocolate and Blommer Kinzie Milk Chocolate) probably won't be found listed on their website. But they've always had it in stock when I needed to place an order.
Give them a call. Their phone number is on the website. It has been my experience that they are happy to take orders by telephone.