Welcome to WebmasterWorld mgmedia! If by "Exit Exchange" you mean a pop-up window, you'll find they're real unpopular with most of the regulars here... But here's a couple good sources for free and inexpensive scripts: [cgi.resourceindex.com...] [simplythebest.net...]
mgmedia - If this is question is a continuation of your question about a script to do pop ups, next time, please add it to the existing thread (aka discussion). Anyone seeing this post, then reading your question isn't gonna have a clue what you're asking about unless they happened to read the original thread.
As to which script to select, perhaps someone else will have a suggestion. My suggestion is to use the "search" feature at each script resource site and find the script that meets your needs.