The cost of this is rather low. Basically you just need a cheap block account (“buy a 5 GB pack and it will never expire until the volume is used”); in most cases only a fraction of your downloads will go through the secondary server, this might even applies for DMCA related problems. For example Blocknews.net offers 5 GB for $2.75 with an acceptable retention.
Next, check if your newsreader has multi-server support, if you can setup more than one server chances are you can use this method. Depending on the program there may be a checkbox saying “backup server” (e.g. SABnzbd+), “fill server” (e.g. Newsbin) or similar, others use a prioritization system where you have to give the backup server a priority lower than the primary one (e.g. Newsleecher) and so on. Check the list below for setup instructions for your newsreader.