I did similar, except mine is in the side of the dash and not in the hood. I got mine from Amazon - Tecmate.
https://www.amazon.com/Tecmate-Opti...s=gateway&sprefix=techmate+SAE,aps,162&sr=8-1
You will also need:
https://www.amazon.com/Battery-Tend...817Z660CRWS&psc=1&refRID=V9D163Z79817Z660CRWS
I have a pickup I do not drive much (2,000 miles a year.) I had the battery go dead a few times (Alarm, ecu-vehicles do not truly shut off 100% anymore) so I installed one these on t as well, in the bumper in a cavity. Battery is 100% every time now.
My tractor does not get as much use as I'd like, last year, just ten run time hours. Also, I do not have power where it is stored so... no ability to plug it in to a maintainer. I did install a voltmeter on it. Over the last year, the voltage has dropped to under 12 volts. 11.8 yesterday and I could noticably tell it was not a happy camper, it just started. It will not start once it gets cold. New battery in the next thirty days. The existing one is just three years old.