The company that makes these is called Flambeau What I linked above is a 4qt tank but they do have larger and smaller tanks.
http://fluids.flambeau.com/standard_...4.0_quart.html
Using 2 tanks one large and one small is not a bad idea, one larger supply tank feeding a smaller delivery tank located lower then the larger supply tank might help cut down on the sloshing since the smaller tank if fitted correctly should be almost filled up all the time. If you do get a smaller tank to run with the larger tank make sure to get a sealed cap with it and not vented.