The SDRPlay can be purchased at your local Ham Radio Outlet.
I would say that the 2 front runners in the lower-end SDR world are the SDRPlay and the Airspy. The Airspy is only available online, to my knowledge.
Beyond those 2, you are heading towards the $1000+ range.
In addition to an SDRPlay, I have numerous RTL dongles which are not the best. However, I find that for the price, they work pretty darn good, especially decoding digital voice and data. Some people hate 'em, but I find that they work great - DSDPlus and 2 RTLSDR's are hard to beat for under $50.
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