Davvin is a pretty old and dated book (and not that good, if you ask me). Your best bet would probably be a second-hand bookshop somewhere in Sweden.
Also, this person states in his
blog about a North Saami course that: "Kursen baserar sig på Davvin 1, men eftersom boken inte längre finns till salu kommer ett nytt material att utarbetas och finnas till salu vid första lektionstillfället." (= "The course is based on Davvin 1, but because the book is no longer for sale, new material will be developed and available for purchase in the first lesson.")