There are usually used copies available on Alibris, Abebooks, and Amazon. Most of them are "much-loved", as you might imagine! I got my copy this way several years ago, and found that the edition had a few more pages of options for Bobbie than I had in my childhood version. Also, the author is Frieda Friedman, which may help widen the search, if needed. Look under "Bobby" and "Bobbie", though the latter is the correct spelling.
When I was little, my mother would read this to me, and sing a carousel-like song when she got to the merry-go-round page (actually, it was the Skater's Waltz).
Hi, I was also looking for this book to get for my neice as a gift - it took ages to find but there is an antique bookshop in New Jersey called 'Between the Covers' and they had a copy. They are very helpful so if you contact them, they may have it.