Well, you can’t.
Engineer Bob offered a link days ago which I forgot to put it up. Meanwhile that company sold out of their (networkable!) GM instruments. My bad.
You probably can find GM friskers right now. Major companies aren’t likely gouging, either. But unless you must have one immediately, soon you could be in a radiological “Army of Davids“.
The story is at Watt’s Up With That. (An excellent climate blog)