Yes when Radio Shack went out of business I picked up fistfuls of them for $5 a piece. The antenna was originally made by GRE who was making the radios for Radio Shack at that time. When GRE went out of business, supposedly a GRE employee started the remtronix company. It is the same antenna except they made the Improvement of the water-resistant mount that fits the proprietary antenna connection on the SDS 100.
Poster... If you live in a house you might as well buy a good rooftop antenna of your choice. Plenty of suggestions here on RR depending what route you want to go, get some good quality coax like lmr400 and mount a rooftop antenna with a good ground and good waterproofing. Meanwhile, back at the ranch I think you will see a world of difference with the remtronix antenna. It's a well-proven performer.