My guess is that something like that can be bought for a very little amount of money. Palmer Cab Merger is the name. I am not sure if something similar is availably by radial... So no need for soldering.
As well there are some cabs that have that as a standard feature (bluguitar cabs)...
You can most certainly buy it, but if you're not afraid of solder you can save the $50
Also with that box that you referenced you could accidentally plug into the parallel Jack and blow the amp on the Kemper.
the solder! Solder is our friend lol.