I recently received and assembled a Nixie Clock Kit (not my kit) for my birthday. However, there's a 180V no-touch area. With 2 kids, I wanted to build in a little extra safety to keep fingers from wandering into the danger zone. It also helps to block out stray light since I use it as a bedside clock. If you use ABS and polish it, it also reflects a little bit of light inside the clock that gives it a cool effect. Black works well, but I bet a translucent (t-glase or similar) filament would look pretty good too.
3D model and more available at [ thingiverse.com ].