Just popping in to update, after a bit of googling, I've decided and just bought a KR-Multicase double backpack and a KR Standard Aluminium case. The bag, among other features is waterproof and has chest and waist clips for cyclists and bikers, which sounds perfect and while it fits 2 cases, it can be altered to fit just 1 case (which is what I'm getting for now).
Thanks for the help and the replys.