The Juice Box does not necessarily have two outputs. I make them customized for the different applications. Some only have an input and a 5v output. Some have an input, a pass-through voltage output, and a 5v output. Some have an input and two 5v outputs. Sorry, I don't keep good enough records to know which Bagtag has.
And I'm not sure if I'm understanding you right, but you can't use a JuiceBox to power a UA5. A UA5 takes 9v input (not sure of the exact range) and the JBox supplies 5v. Some customers use a JuiceBox with a pass-thru output to power a UA5 and also a JB3/MT off the same 9v battery, but that is somewhat different. If you are only using a UA5, there is no need for the JBox.
As to cables, I can obviously make them for you, but in general, the JBox uses center-positive DC coaxial plugs, size 5.5mm/2.1mm (adaptaplug M) and the walmart battery takes 4.0mm/2.1mm (size B).