Of course you can always whip up some heavy cream yourself using a mixer and either a sugar substitute or none as you see fit. But there is a better way.
There is a gadget called the ISI Cream Charger. It is a cannister (reddi-whip shaped). You pour in the cream. You add your sweetener/flavorings or not. You put the top on with a charger pellet. Voilla. You now have a can of instant whipped cream with no sugar. It lasts for about 14 days in the refrigerator.