Mineral spring water facial sprays combined with a water-based serum makes for a good alternative. Mineral water contains the ions needed to make conductivity possible on the skin.
Ultrasound conductive gels contain glycols which aren't really good for the skin so avoid those.
Best to use a conductive gel formulated just for microcurrent devices. You can even stretch your dollar by using one along with the mineral water spray to keep it from drying out instead of applying more gel.