Backup my Old Chomp App to SD

So I'm about to perform a factory reset. I'll backup some settings and I have a list of my apps. I have an old version of Chomp SMS that I love (without ads) and I'd like to back it up and reinstall this same version after the reset. I'd rather do this with a free app and have it relinked to the market. Am I asking too much? Anyone have any ideas? The latest version of Chomp sucks, but I still don't want to sever its link to the market. Other apps I can just redownload. I've searched around and it seems like most solutions don't handle the "private" app setting that some apps have. Thanks.