Astroglide is water-based, water-soluble, condom compatible, and petroleum free sexual lubricant. It is made from water, glycerin, proplyne ternimus, methylparaben, and propylparaben. It looks exactly like seminal fluid and tastes like sweet rubbing alcohol. Prices probably vary wildly but around here it costs about $12 for a 2.5 oz. bottle. Larger bottles are available but that should last you quite a while as you don't need much.
It can be used for lubrication during anal sex, vaginal sex, while manually manipulating a penis, or for any other scenario where skin will be rubbing against skin.