New or used depends upon your temperance and budget. I would recommend Ortlieb's (if you like to stuff everything in one bag like me) or Arkel's (better if you like a lot of pockets - I can't remember what pocket I used for what). There are certainly other brands that will work fine. I tried several brands (Axiom, Performance Bike) with shock-cord mounting, then bought a set of Ortlieb's and was done searching.