Is it possible to find a member who has two titles from the same author on their bookshelf?  I've pulled up each title individually then looked at the rest of both members' bookshelves to see if they had the other title, but no such luck.  I'm not necessarily looking for a deal, but is this the type of thing I would post in the Book Bazaar? 

It sounds like they are not Wish Listed so yes, you could post in the Bazaar asking if someone has both. You could also check out the Genre Forum and see if they have a "is this on your bookshelf" type thread to post in.

The search feature for Boxer's is available to everyone, so if there is a Boxer with both of them you could go into the Box-o-Books section and search Boxers' shelves for the author. You'd still have to look at their shelves to see which books by that author they have, but it show which ones have multiple of that author to better your chances.