Many circuit boards are available under nixie clocks but you need the tubes to complete the project. Here is a complete set of 6x (SIX) IN-12 Nixie tubes, 4x (FOUR) INS-1 dot separators plus 6x (SIX) K155ID1 driver chips which you may need if you are making your own circuit.
The tubes are becoming rare and hard to find at a reasonable price. The driver chips are very rare and were especially designed to handle the high voltages of nixie tubes. The INS-1 dot display is interesting and unusual and is better than a simple neon tube as decimal point or dot digit separator because it creates an even dot -see picture.