Vial of mercury can do it. It should be recolored to 4 versions, replace some usefulness artafacts, then give it each time we get a potion. For me it seems to be a good solution, as we can check for number of potions at the start of the battle, looking for artefacts. But there are also other ways. The bad side is that it will take a lot of space, and the backpack has a limited storage. Otherwise the number of potions can be stored in a variable, and checked with right clicking, as for mithril, but will be less interesting visual.