Being from police state of NJ, its probably illegal. I'm interested to hear this also, would be awesome for a party where you want beer en masse of a commercial favorite. I'm sure if you made your own sanke keg adapter a few craft brewers could be persuaded. Plenty of pro-beers are sent out in 5 gal sanke kegs, so they do have pricing for it, at least commercially.
I don't know of any breweries letting you filly your own corny kegs, but I know some breweries sell sixtels, which are all of 0.16 gallons more than a corny. Also you live in Carteret, you can go to the Joe Canals Woodbridge, they have a giant collection of kegs, too many to list.
Ok so JJ Bittings will fill corny kegs Mike from JJ's stated they do it all the time and to contact the brewer. Harvest moon in NB will also "however, you would have to drop it off and pick it up another time as Sunday’s are my only day off(although this Sunday we are actually bottling the barrel aged beers). Also, I don’t have any corny fittings as all of our kegs are American Sankey style so I would need you to drop off the fittings with the keg.
You could certainly drop it off one Sunday and pick it up the next. If you wanted to come back during the week to pick it up, that is also ok, I would just need know when you planned on picking it up so I can be sure to have it ready.
The only other thing is it would be best to check with me in advance, as the availability of beers would depend on how much we currently have on hand. I should always be able to fill it but maybe not always with your first or second choice.
Harvest Moon Brewery/Café
392 George St.
New Brunswick, NJ 08901