From the factory you probably have one or two nuts and bolts between the frame and base of the tank which is pretty unsubstantial. You can get the long bolt to handle type for a single tank on Amazon or at a local RV parts store.
Our first upgrade on our old pup was to dual tanks, and that required a more substantial tank rack that held two tanks securely.
Do a quick search on here; there was a thread on this within the last two weeks with several pictures of various solutions.
2011 Jayco X19H (purchased 2015)
2008 Jayco 1007 PUP (purchased new, traded for the X19)
2012 Chev Traverse LT with TP