It is available on Amazon. I would assume you can get it in a bookstore if it is available there.
I almost never shop online but since I haven't seen a copy in a bookstore in years I may break down and order one, now that my "M*A*S*H Mania" has hit a new high in my old age.
M*A*S*H Mania is another book I wish was still available, but alas it's been out of print almost 40 years now... one of the Hooker novels I never have been able to get my hands on, and for sure the third best of the sequels, the last book of the series and the one where Hooker returns to apparently write it all himself.
I have found on Goodreads site a pretty nice set of synopsis/critiques, including cover scans and other information on the books. Here's the one on M*A*S*H Mania for example:
Well, that one's a little skimpy compared to the reviews of the first couple, here's their list of all 15 books, yeah, there were 14 "After M*A*S*H" books, with 5 or 6 that come out in 1976 alone!