Those bags sem to look OK but I suppose you won't know how well they work until you try them. I have heaps of freezer blocks so I use those instead of ice which makes things very easy.
Last weekend I had 2 kegs of rather poor beer and so I unleashed them on some unsuspecting friends. I used an esky as the party keg cooler and this worked a treat. I only needed 2 freezer blocks in the esky. I kept the other keg in a 100 Can Cooler with the remainder of the freezer blocks. Kegs remained perfectly cold until they were finished 12 hours later in about 25 dgree ambient heat.
The main thing is to make sure your keg starts out cold. I have also used the 100 Can Cooler for the same purpose and this works fine over a 6 hour period.
You can get a general idea of how I worked the esky as a party keg cooler here. I reckon a corny keg would fit in that esky as well.
WASTE OF MONEY
they will not fit our cornies not being a kill joy but on the bright side if you go to a wetsuit maker they will make you a keg jacket with velcro fly for around the same price $35 bucks .I had one made years ago before i was married and stopped brewing for a bit i sold off all that gear but now i have started again in the last 4 years might get one made up for the fermenter ?? as the kegs live in the fridge now.