Ah, I hadn't realised that the Leyline component was so cheap to include. Okay, it's not worth making a rivers-only version. A cheap Leyline-only version and an expensive Leyline-only version should be good enough, unless the thread unexpectedly decides to look into Material transmission.
(Which wouldn't be the worst thing in the world, mind you - even if we never make a Waystone with it, the chance to learn how these various extremely knowledgeable magic-users manage that could be extremely useful for enchanting someday.)