Here is one of the tiniest Nixie Tube clocks money can buy. The TiNixie has an alarm/timer function and runs on a 500mAh battery. It uses IN-17 Nixie Tubes. You can deactivate the alarm and display time with a tap. This clock has a customizable RGB backlight.
The TiNixie has a magnetic charger in the back. It measures 40 x 40 x 40mm.