Unfortunately I can't seem to find any frequency counters on ebay that are under $100 except for the cheap Chineseum kits, but they don't have a case and they require a 9V battery to operate and use a WiFi Antenna style input plug, and they don't seem to have any sort of adjustments on them like the factory built ones that are going for over $100 and as much as $25,000 for a Hewlett-Packard Agilent model from the 1970s...
