I have looked into this before and apparently the GSXR (forgot which year) is the 2nd hand (inexpensive) unit to get.
Saying that there's a lot more experienced people on here that will tell you a steering dampener is not needed on a 919, as its an extremely stable bike. If you are getting headshakes, etc., there's most probably something else wrong, like tyres, or suspension.
If you just want it as a trick/ fun mod, why not, do what makes you happy.:001_smile:
Just had a look at that e-bay link. Personally if it is what I think it is, I wouldn't put a cheap chinese knock-off/generic steering dampener on my bike, its asking for trouble, IMO.