Would a generic file sharing and hosting site work? If you place the file in a public Dropbox folder and reference it from your site? See the Web Applications Stack Exchange for more online file storage providers.
Make sure you check the Cross-domain policy: if the Flash file hosted on dropbox.com needs to access data from yourdomain.com, you need a crossdomain.xml file on yourdomain.com that specifies that Flash files from dropbox.com are allowed to access data.