OK, understood. Well, there's no direct equivalent to 6511 that I'm aware of, eg with variable K factors etc though amongst the specialist ag/turf software there may well be something that can ingest data from a WL logger and do much the same thing as 6511, very probably more (though very likely with a larger price-tag too).
But AFAIK 6511 has not been discontinued. I'm guessing Ryan should be able to get a pack when he next reorders Davis stock or eg it seems to be available direct from Davis, though inevitably at a higher price.