I have rid my garage of several red squirrels and zapped one large "regular squirrel" with the rat zapper. Just a little peanut butter on a plastic water bottle cap at the back of the trap. It's also been very effective on mice.
https://www.amazon.com/Victor-RZC001-Zapper-Classic-Trap/dp/B002665ZTC
https://www.amazon.com/Victor-RZC001-Zapper-Classic-Trap/dp/B002665ZTC