Every Arpilo piece is lit by an ordinary flameless LED tealight. This page is everything about it.
A warm-white flameless tealight, 37.5-38 mm across, with its cell installed. Keep it: it is the measurement for the next one.
Any flameless LED tealight 37.5-38 mm across. They are sold in packs of 12 or 24 at hardware stores, dollar stores and online for well under a dollar each. Warm white looks like a flame; cool white looks like a fridge. Get warm.
If you want longer nights, a rechargeable set (six lights, one charging tray, a remote) fits the same seat. They are a little dimmer than a fresh coin-cell light, and the stone was calibrated for the dim end, so it still works.
Never a flame. The stone is a plastic and a candle will melt it. The warning is embossed on the inside of every piece, where you will never see it unless you look.
It lifts out. The night light loads from the top; the slab and the nodule lift off their bases. Nothing unscrews, nothing unclips, and there is nothing to break.