Today I finally installed one.
Despite these being in the NEC for a few years, local supply houses had none in stock -- and couldn't recall ever selling one. After an tended wait, an internet vendor sent me one. A Square D Homeline (HOM2175SB), it cost about $120.
With the decrepit state of the local PoCo grid and the frequency of lightning here, I have wanted to have surge suppression for at least a decade,
Ordering one in the past -- despite their being listed in catalogs and featured in the trade press -- was simply not possible. A request to the supply house invariably resulted in a chat with Square D's engineering department. Such calls always resulted in Square D professing complete ignorance of the topic, and wanting all manner of technical specs such as the impedance of the PoCo transformer and such.
Looking at the instructions I found two matters worthy of comment.
First, Square D is careful to note that their product "may not suppress surges for electronic equipment." Sort of makes me wonder how they know where the electricity is going
Second, there is discussion of what to do with the coiled white wire coming off the device. While the artwork does show the wire landed on the neutral buss, there is no mention of straightening or shortening the wire.
As there is no reset button or trip indicator, I infer that this device simply gives surges a clear path to ground, thereby reducing your equipments' exposure to the surge. Sort of like French unions, the thing just sits around waiting for a strike, then carries on like nothing happened (Sorry, I couldn't resist!)