You want a new one or old one? A modern one that's nice is the GQ GMC-600 Plus Geiger Counter Alpha, Gamma, Beta X-Ray Radiation Monitor. You can even export it's readings to an Excel spreadsheet. The price defines how much it does, so there's a range of models and prices. That one is around $325 on E-Bay. If you want some fun and look like you're running from a nuclear apocalypse, you can find one of those old surplus Civil Defense metal yellow ones for $99 on E-Bay as well.
I've got a Vasoline (uranium) glass collection. That stuff sets off Geiger counters and glows bright in UV light.
Cat (n.) A bipolar creature which would as soon gouge your eyes out as it would cuddle.