There are... many people DIY them, but they can be found for sale online. I've seen them on eBay. Also, www.socaltropicalfishoutlet.com sells ones made by a local shop.Hmm theres got to be some type of acrylic device which somebody makes that can hang on the ledge of the sump and then have holes in it for probes. Kind of like the way a tunze osmolator hangs in the sump...???
Made it myselfRussm did you fabricate the probe holder or did you buy that from a vendor?