I have this one:
http://www.boatandrvaccessories.com/battery-tender-021-0128-battery-charger.html?cmp=googleproducts&kw=battery-tender-021-0128-battery-charger&gclid=Cj0KEQiAuf2lBRDW07y3z6f96awBEiQA0IngJshUjbRPQohaY8WOmzQ0q3auYiUH82IyPUMefLZwlh4aAs728P8HAQ
I can't remember where I got it. I...