Been awhile since my last update but acquired another boxed set:
Books 41-44 (Complete):
#41 Bad Hare Day
#42 Egg Monsters From Mars
#43 The Beast From The East
#44 Say Cheese and Die-Again
This leaves me with #45-#48 boxed set left to acquire. After that I believe Goosebumps went away from the boxed sets and sold the remaining books as singles.
Search continues!