Above replies are spot on ...
To be honest in my view - the P3-4K was a stop-gap version to try and bridge the starter Standard to the Advanced / Pro versions. I really cannot see the point of it when P3 Pro versions are out there for same money.. in fact less if you are willing like I was to buy 2nd hand.
The Adv and Pro versions of the P3 are far better than the P3-4K .... apologies to 4k owners but that's my opinion.
Where to find ? Local adverts, Craigslist, etc. Mine was via local advert ... I was able to meet, test, fly, check the dat files etc. before handing over the money. I rec'd not only the P3P, but a hard case, extra props, extra battery etc. For less money than you say for the P3-4K
Nigel