The link covers DC to DC Converters you will need to plug this in so it gets the right voltage.
Most of the stuff that we have is convertible to Solar Pluggables.
To Buy this stuff in an RV store, if you can, will be a very expensive proposition.
Hawai'i does not even have an RV store, where we gonna drive to?
We do have a boat supply store that supplies many high priced Jim Cracks and Thing Ah Ma Bobs if ya like gettin' raped on the price.
This 'Cassio Label It' uses 4 AA batteries and I don't like to buy batteries.
Not even Rechargeables.
So I did a little surgery. . .
Step 1: Surgery
Then crack the case open to ID the + and the - wires and what battery contact they go to.
This usually involves taking out the screws that hold the 2 halves of the case together to get at the circuit board.
(sorry no picture here but real easy to do)
The wires you want are easy to find because they go to 2 battery contacts in the battery compartment from the circuit board.
The wires are not necessarily black and red.
Mine were grey (-) and white (+).
First cut those wires as close as you can to the battery contacts in the battery compartment.
Then pull out the contacts, destroy them if you need to.
You won't need them anymore.
Drill 2 holes to fit the White and Grey wires through to the battery compartment.
Solder your choice of DC line cord to White + and Grey -. Mind the Polarity on the cord.
Drill a hole in the battery compartment cover to push the DC line cord through to the outside.
I tied a knot in the cord as a strain relief.
No rubber grommet needed.