There are numerous private label GC2 batteries, but only a couple companies actually making them. Those are flooded cell rather than AGM, so that narrows it down to US Battery or Johnson Controls, and both of those manufacturers are excellent at the GC2 type. Trojan also makes flooded cell GC2, but they never sell under a private label and their cases are dark red.
Flooded cell GC2's come in two basic amp-hour capacities, either 210 or 230 AH. If you never boondock, choose the lesser one and save a few bucks (and a few lbs of weight). Otherwise get the 230 AH size. Sams Club and Costco have excellent prices on them.
If you want less maintenance, change to AGM Gc2. No water to check & add, but they cost about double.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL