ontf,
I was disappointed to learn that Solar Converters closed as well. We use several of their converters. Good quality & reasonable prices; this leaves a void.
There are, however several voltage control relays/controls around. We've been using an Omron voltage sensing relay for high limit on our turbine. The model we have has been discontinued, but there must be a model that supersedes ours (K8AB-VS). I would look at Allied Electronics, Mouser, Digi-key or Newark. You might also find something on one of the alternative energy providers like Backwoods Solar, Kansas Wind Power or AltE Store.
I know that some of the Solar Converters stock is still around - AltE and John Drake (aka Solar Seller) are couple places I've noted. Good luck.
~ks