You could actually create that directory on the web server and add a page called default.aspx in that directory and set the file up to do a 301 permanent redirect to the appropriate page in Dotnetnuke. That would probably be the simplest solution.
You could also look at the formulas for url's to try to resolve that page to the appropriate page, but I've not done that before and don't know anything about how to create such a formula, only that it may or may not be possible.
Another solution might be a third party url module like "ifinity", but I'm not sure if that would work either. Of course, you'd want to bill the cost of such a module to the person who created the fliers. ;)
I think the 301 redirect with an actual page created outside the dnn platform is going to be the easiest. DNN won't have problems with foreign files stuck in there, it will just ignore them. I've actually had dnn set up in a root folder with a php script based website in a subdirectory and both worked fine, they just ignored each other. Well, as an added bonus a dnn backup module that was set to back up the physical files also backed up the php directory, other than that there was no interaction or interference either. I've also done this when converting one website over to dnn, I actually placed all the current sites aspx files in the dnn root with 301 redirects to the new dnn page to avoid any issues with search engines not finding the pages, and then there was no need to resubmit anything to search engines either.