FYI waxed linen has a tendency to mildew, so it's best and cheaper to make your own waxed linen covers to replace the yucky mildewed covers.
The linen wax is a combination of beeswax and boiled linseed oil. Some recipes include a bit of paraffin wax, too. Plenty of recipes online for the correct proportion of each, can't remember off the top of my head. Wax dries hard and it crumbles. BLO makes the beeswax flexible.
Put the linen circles on a bed of paper towels. Melt the wax mixture and paint the linen with a disposable brush. Then use a heat gun to even out the wax. The excess wax drips through into the paper towels.